Search: a004831 -id:a004831
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A000583
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Fourth powers: a(n) = n^4.
(Formerly M5004 N2154)
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+10
399
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0, 1, 16, 81, 256, 625, 1296, 2401, 4096, 6561, 10000, 14641, 20736, 28561, 38416, 50625, 65536, 83521, 104976, 130321, 160000, 194481, 234256, 279841, 331776, 390625, 456976, 531441, 614656, 707281, 810000, 923521, 1048576, 1185921
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OFFSET
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0,3
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COMMENTS
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Figurate numbers based on 4-dimensional regular convex polytope called the 4-measure polytope, 4-hypercube or tesseract with Schlaefli symbol {4,3,3}. - Michael J. Welch (mjw1(AT)ntlworld.com), Apr 01 2004
Totally multiplicative sequence with a(p) = p^4 for prime p. - Jaroslav Krizek, Nov 01 2009
The binomial transform yields A058649. The inverse binomial transforms yields the (finite) 0, 1, 14, 36, 24, the 4th row in A019538 and A131689. - R. J. Mathar, Jan 16 2013
Generate Pythagorean triangles with parameters a and b to get sides of lengths x = b^2-a^2, y = 2*a*b, and z = a^2 + b^2. In particular use a=n-1 and b=n for a triangle with sides (x1,y1,z1) and a=n and b=n+1 for another triangle with sides (x2,y2,z2). Then x1*x2 + y1*y2 + z1*z2 = 8*a(n). - J. M. Bergot, Jul 22 2013
For n > 0, a(n) is the largest integer k such that k^4 + n is a multiple of k + n. Also, for n > 0, a(n) is the largest integer k such that k^2 + n^2 is a multiple of k + n^2. - Derek Orr, Sep 04 2014
Does not satisfy Benford's law [Ross, 2012]. - N. J. A. Sloane, Feb 08 2017
a(n+2)/2 is the area of a trapezoid with vertices at (T(n), T(n+1)), (T(n+1), T(n)), (T(n+1), T(n+2)), and (T(n+2), T(n+1)) with T(n)=A000292(n) for n >= 0. - J. M. Bergot, Feb 16 2018
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REFERENCES
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R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1990, p. 255; 2nd. ed., p. 269. Worpitzky's identity (6.37).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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G.f.: x*(1 + 11*x + 11*x^2 + x^3)/(1 - x)^5. More generally, g.f. for n^m is Euler(m, x)/(1-x)^(m+1), where Euler(m, x) is Eulerian polynomial of degree m (cf. A008292).
E.g.f.: (x + 7*x^2 + 6*x^3 + x^4)*e^x. More generally, the general form for the e.g.f. for n^m is phi_m(x)*e^x, where phi_m is the exponential polynomial of order n. - Franklin T. Adams-Watters, Sep 11 2005
a(n) = C(n+3,4) + 11*C(n+2,4) + 11*C(n+1,4) + C(n,4). [Worpitzky's identity for powers of 4. See, e.g., Graham et al., eq. (6.37). - Wolfdieter Lang, Jul 17 2019]
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) + 24. - Ant King, Sep 23 2013
Sum_{n>=1} (-1)^(n+1)/a(n) = 7*Pi^4/720 (A267315).
Product_{n>=2} (1 - 1/a(n)) = sinh(Pi)/(4*Pi). (End)
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MAPLE
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A000583:=-(z+1)*(z**2+10*z+1)/(z-1)**5; # Simon Plouffe in his 1992 dissertation; gives sequence without initial zero
with (combinat):seq(fibonacci(3, n^2)-1, n=0..33); # Zerinvary Lajos, May 25 2008
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MATHEMATICA
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PROG
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(Haskell)
a000583 = (^ 4)
a000583_list = scanl (+) 0 a005917_list
(Maxima) makelist(n^4, n, 0, 30); /* Martin Ettl, Nov 12 2012 */
(Python)
def a(n): return n**4
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CROSSREFS
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KEYWORD
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nonn,core,easy,nice,mult
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AUTHOR
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STATUS
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approved
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A047217
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Numbers that are congruent to {0, 1, 2} mod 5.
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+10
25
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0, 1, 2, 5, 6, 7, 10, 11, 12, 15, 16, 17, 20, 21, 22, 25, 26, 27, 30, 31, 32, 35, 36, 37, 40, 41, 42, 45, 46, 47, 50, 51, 52, 55, 56, 57, 60, 61, 62, 65, 66, 67, 70, 71, 72, 75, 76, 77, 80, 81, 82, 85, 86, 87, 90, 91, 92, 95, 96, 97, 100, 101, 102, 105, 106, 107, 110, 111
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OFFSET
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1,3
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COMMENTS
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Also, the only numbers that are eligible to be the sum of two 4th powers (A004831). - Cino Hilliard, Nov 23 2003
Nonnegative m such that floor(2*m/5) = 2*floor(m/5). - Bruno Berselli, Dec 09 2015
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LINKS
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FORMULA
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G.f.: x^2*(1+x+3*x^2)/(1-x)^2/(1+x+x^2). - Colin Barker, Feb 17 2012
a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.
a(n) = (15*n-21-6*cos(2*n*Pi/3)+2*sqrt(3)*sin(2*n*Pi/3))/9.
a(3*k) = 5*k-3, a(3*k-1) = 5*k-4, a(3*k-2) = 5*k-5. (End)
Sum_{n>=2} (-1)^n/a(n) = sqrt(1-2/sqrt(5))*Pi/5 + 3*log(2)/5. - Amiram Eldar, Dec 10 2021
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MAPLE
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seq(op([5*i, 5*i+1, 5*i+2]), i=0..100); # Robert Israel, Sep 02 2014
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MATHEMATICA
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Select[Range[0, 120], MemberQ[{0, 1, 2}, Mod[#, 5]]&] (* Harvey P. Dale, Jan 20 2012 *)
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PROG
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(PARI) concat(0, Vec(x^2*(1+x+3*x^2)/(1-x)^2/(1+x+x^2) + O(x^100))) \\ Altug Alkan, Dec 09 2015
(Magma) I:=[0, 1, 2, 5]; [n le 4 select I[n] else Self(n-1)+Self(n-3)-Self(n-4): n in [1..70]]: // Vincenzo Librandi, Apr 25 2012
(Magma) &cat [[5*n, 5*n+1, 5*n+2]: n in [0..30]]; // Bruno Berselli, Dec 09 2015
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CROSSREFS
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Cf. similar sequences with formula n+i*floor(n/3) listed in A281899.
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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A002645
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Quartan primes: primes of the form x^4 + y^4, x > 0, y > 0.
(Formerly M5042 N2178)
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+10
23
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2, 17, 97, 257, 337, 641, 881, 1297, 2417, 2657, 3697, 4177, 4721, 6577, 10657, 12401, 14657, 14897, 15937, 16561, 28817, 38561, 39041, 49297, 54721, 65537, 65617, 66161, 66977, 80177, 83537, 83777, 89041, 105601, 107377, 119617, 121937
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OFFSET
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1,1
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COMMENTS
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The largest known quartan prime is currently the largest known generalized Fermat prime: The 1353265-digit 145310^262144 + 1 = (145310^65536)^4 + 1^4, found by Ricky L Hubbard. - Jens Kruse Andersen, Mar 20 2011
Primes of the form (a^2 + b^2)/2 such that |a^2 - b^2| is a square. - Thomas Ordowski, Feb 22 2017
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REFERENCES
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A. J. C. Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929; see Vol. 1, pp. 245-259.
N. D. Elkies, Primes of the form a^4 + b^4, Mathematical Buds, Ed. H. D. Ruderman Vol. 3 Chap. 3 pp. 22-8 Mu Alpha Theta 1984.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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A. J. C. Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929. [Annotated scans of a few pages from Volumes 1 and 2]
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FORMULA
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EXAMPLE
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a(1) = 2 = 1^4 + 1^4.
a(2) = 17 = 1^4 + 2^4.
a(3) = 97 = 2^4 + 3^4.
a(4) = 257 = 1^4 + 4^4.
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MATHEMATICA
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nn = 100000; Sort[Reap[Do[n = a^4 + b^4; If[n <= nn && PrimeQ[n], Sow[n]], {a, nn^(1/4)}, {b, a}]][[2, 1]]]
With[{nn=20}, Select[Union[Flatten[Table[x^4+y^4, {x, nn}, {y, nn}]]], PrimeQ[ #] && #<=nn^4+1&]] (* Harvey P. Dale, Aug 10 2021 *)
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PROG
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(PARI) upto(lim)=my(v=List(2), t); forstep(x=1, lim^.25, 2, forstep(y=2, (lim-x^4)^.25, 2, if(isprime(t=x^4+y^4), listput(v, t)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 05 2011
(PARI) list(lim)=my(v=List([2]), x4, t); for(x=1, sqrtnint(lim\=1, 4), x4=x^4; forstep(y=1+x%2, min(sqrtnint(lim-x4, 4), x-1), 2, if(isprime(t=x4+y^4), listput(v, t)))); Set(v) \\ Charles R Greathouse IV, Aug 20 2017
(Haskell)
a002645 n = a002645_list !! (n-1)
a002645_list = 2 : (map a000040 $ filter ((> 1) . a256852) [1..])
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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More terms from Victoria A Sapko (vsapko(AT)canes.gsw.edu), Nov 07 2002
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STATUS
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approved
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A018786
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Numbers that are the sum of two 4th powers in more than one way.
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+10
10
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635318657, 3262811042, 8657437697, 10165098512, 51460811217, 52204976672, 68899596497, 86409838577, 138519003152, 160961094577, 162641576192, 264287694402, 397074160625, 701252453457, 823372979472, 835279626752
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OFFSET
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1,1
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COMMENTS
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Since 4th powers are squares, this is a subsequence of A024508, the analog for squares. Sequence A001235 is the analog for third powers (taxicab numbers). Sequence A255351 lists max {a,b,c,d} where a^4 + b^4 = c^4 + d^4 = a(n), while A255352 lists the whole quadruples (a,b,c,d). - M. F. Hasler, Feb 21 2015
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, D1.
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LINKS
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FORMULA
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EXAMPLE
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a(1) = 59^4 + 158^4 = 133^4 + 134^4.
a(2) = 7^4 + 239^4 = 157^4 + 227^4. Note the remarkable coincidence that here all of {7, 239, 157, 227} are primes. The next larger solution with this property is 17472238301875630082 = 62047^4 + 40351^4 = 59693^4 + 46747^4. - M. F. Hasler, Feb 21 2015
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MATHEMATICA
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Select[ Split[ Sort[ Flatten[ Table[x^4 + y^4, {x, 1, 1000}, {y, 1, x}]]]], Length[#] > 1 & ][[All, 1]] (* Jean-François Alcover, Jul 26 2011 *)
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PROG
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(PARI) n=4; L=[]; for(b=1, 999, for(a=1, b, t=a^n+b^n; for(c=a+1, sqrtn(t\2, n), ispower(t-c^n, n)||next; print1(t", ")))) \\ M. F. Hasler, Feb 21 2015
(PARI) list(lim)=my(v=List()); for(a=134, sqrtnint(lim, 4)-1, my(a4=a^4); for(b=sqrtnint((4*a^2 + 6*a + 4)*a, 4)+1, min(sqrtnint(lim-a4, 4), a), my(t=a4+b^4); for(c=a+1, sqrtnint(lim, 4), if(ispower(t-c^4, 4), listput(v, t); break)))); Set(v) \\ Charles R Greathouse IV, Jul 12 2024
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A351306
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Least positive integer m such that m^4*n = u^4 + v^4 - (x^4 + y^4) for some nonnegative integers u,v,x,y with x^4 + y^4 <= m^4*n^2.
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+10
5
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1, 1, 1, 10, 2, 2, 2, 4, 6, 4, 2, 2, 4, 8, 1, 1, 1, 1, 2, 2, 2, 2, 10, 2, 2, 2, 2, 10, 10, 2, 1, 1, 1, 2, 2, 2, 2, 8, 2, 2, 2, 2, 2, 10, 2, 2, 1, 1, 5, 1, 1, 4, 10, 10, 2, 2, 6, 10, 4, 4, 2, 4, 1, 3, 1, 1, 1, 10, 2, 2, 2, 2, 2, 2, 4, 2, 2, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 4, 10, 2, 2, 4, 6, 6, 1, 1, 1, 1, 5, 2, 2
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OFFSET
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0,4
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COMMENTS
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Conjecture: Each n >= 0 can be written as u^4 + v^4 - (x^4 + y^4), where u,v,x,y are rational numbers with x^4 + y^4 <= n^2. In other words, a(n) exists for any nonnegative integer n.
A known result of R. Norrie states that any rational number can be written as u^4 + v^4 - (x^4 + y^4) with u,v,x,y rational numbers.
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LINKS
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EXAMPLE
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a(3) = 10 with 10^4*3 = 8^4 + 13^4 - (4^4 + 7^4) and 4^4 + 7^4 <= 10^4*3^2.
a(242) = 15 with 15^4*242 = 73^4 + 153^4 - (36^4 + 154^4) and 36^4 + 154^4 <= 15^4*242^2.
a(248) = 28 with 28^4*248 = 95^4 + 270^4 - (52^4 + 269^4) and 52^4 + 269^4 <= 28^4*248^2.
a(313) = 30 with 30^4*313 = 37^4 + 128^4 - (7^4 + 64^4) and 7^4 + 64^4 <= 30^4*313^2.
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MATHEMATICA
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QQ[n_]:=QQ[n]=IntegerQ[n^(1/4)];
tab={}; Do[m=1; Label[bb]; k=m^4; Do[If[QQ[k*n+x^4+y^4-z^4], tab=Append[tab, m]; Goto[aa]],
{x, 0, m*(n^2/2)^(1/4)}, {y, x, (k*n^2-x^4)^(1/4)}, {z, 0, ((k*n+x^4+y^4)/2)^(1/4)}]; m=m+1; Goto[bb]; Label[aa], {n, 0, 100}]; Print[tab]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A351341
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Least nonnegative integer m such that n = x^4 + y^4 - (z^3 + m^3) for some nonnegative integers x,y,z with z <= m.
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+10
4
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0, 0, 0, 63, 3, 3, 4, 2, 2, 2, 4, 21, 37, 6, 1, 1, 0, 0, 4, 11, 7, 14, 5, 2, 2, 4, 8, 3, 3, 5, 1, 1, 0, 4, 4, 45, 5, 5, 11, 6, 6, 6, 32, 3, 7, 11, 3, 3, 6, 8, 8, 48, 13, 3, 3, 3, 6, 6, 31, 20, 93, 55, 3, 49, 33, 2, 2, 5, 5, 3, 3, 4, 2, 2, 2, 69, 17, 29, 11, 1, 1, 0, 0, 5, 61, 29, 8, 5, 2, 2, 4, 21, 29, 51, 6, 1, 1, 0, 4, 85, 13
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OFFSET
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0,4
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COMMENTS
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Conjecture 1: Let k be 4 or 5. Then each integer can be written as x^k + y^k - (z^3 + w^3) with x,y,z,w nonnegative integers.
Two examples for k = 5: -4 = 58^5 + 76^5 - (775^3 + 1397^3) and 14 = 40^5 + 67^5 - (125^3 + 1132^3).
Conjecture 2: Let k be among 4, 5, 6 and 7. Then any integer can be written as x^k + y^k - (z^2 + w^2) with x,y,z,w nonnegative integers.
Examples for k = 6, 7: 170 = 9^6 + 15^6 - (2114^2 + 2730^2) and 469 = 7^7 + 8^7 - (1001^2 + 1385^2).
Conjecture 3: For any integer k > 3, there are no nonnegative integers x,y,z,w such that x^k + y^k - (z^k + w^k) = 3.
See also another similar conjecture in A351338.
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LINKS
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EXAMPLE
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a(60) = 93 with 60 = 25^4 + 27^4 - (49^3 + 93^3).
a(527) = 527 with 527 = 29^4 + 110^4 - (91^3 + 527^3).
a(2198) = 1704 with 2198 = 85^4 + 304^4 - (1539^3 + 1704^3).
a(4843) = 1965 with 4843 = 142^4 + 338^4 - (1804^3 + 1965^3).
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MATHEMATICA
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QQ[n_]:=IntegerQ[n^(1/4)];
tab={}; Do[m=0; Label[bb]; k=m^3; Do[If[QQ[n+k+x^3-y^4], tab=Append[tab, m]; Goto[aa]], {x, 0, m}, {y, 0, ((n+k+x^3)/2)^(1/4)}]; m=m+1; Goto[bb]; Label[aa], {n, 0, 100}]; Print[tab]
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CROSSREFS
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Cf. A000578, A000583, A000584, A001014, A001015, A001481, A004831, A004999, A351306, A351321, A351338.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A347824
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Number of ways to write n as x^4 + y^4 + (z^2 + 23*w^2)/16, where x,y,z,w are nonnegative integers with x <= y.
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+10
3
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1, 2, 3, 3, 3, 2, 2, 1, 2, 3, 3, 2, 2, 3, 3, 1, 3, 4, 6, 4, 4, 1, 1, 2, 4, 7, 6, 4, 5, 6, 2, 2, 5, 5, 4, 3, 4, 3, 4, 3, 6, 8, 3, 4, 4, 2, 2, 3, 8, 5, 6, 2, 6, 5, 5, 6, 7, 2, 3, 4, 2, 2, 2, 4, 7, 5, 4, 1, 5, 3, 4, 7, 4, 6, 5, 4, 2, 1, 5, 5, 7, 7, 7, 6, 5, 3, 5, 4, 7, 7, 5, 4, 2, 5, 11, 7, 6, 9, 11, 5, 5
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OFFSET
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0,2
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COMMENTS
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Conjecture: a(n) > 0 for all n = 0,1,2,....
This has been verified for n up to 2*10^6. See also A347827 for a further refinement.
It seems that a(n) = 1 only for n = 0, 7, 15, 21, 22, 67, 77, 137, 252, 291, 437, 471, 477, 597, 1161, 4692, 7107.
For m = 32, 48, we also conjecture that every n = 0,1,2,... can be written as x^4 + y^4 + (z^2 + 23*w^2)/m, where x,y,z,w are nonnegative integers.
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LINKS
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EXAMPLE
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a(7) = 1 with 7 = 0^4 + 1^4 + (2^2 + 23*2^2)/16.
a(15) = 1 with 15 = 1^4 + 1^4 + (1^2 + 23*3^2)/16.
a(67) = 1 with 67 = 1^4 + 2^4 + (15^2 + 23*5^2)/16.
a(477) = 1 with 477 = 0^4 + 2^4 + (27^2 + 23*17^2)/16.
a(597) = 1 with 597 = 2^4 + 4^4 + (5^2 + 23*15^2)/16.
a(1161) = 1 with 1161 = 2^4 + 2^4 + (89^2 + 23*21^2)/16.
a(4692) = 1 with 4692 = 2^4 + 5^4 + (248^2 + 23*12^2)/16.
a(7107) = 1 with 7107 = 1^4 + 5^4 + (239^2 + 23*45^2)/16.
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MATHEMATICA
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SQ[n_]:=SQ[n]=IntegerQ[Sqrt[n]];
tab={}; Do[r=0; Do[If[SQ[16(n-x^4-y^4)-23z^2], r=r+1], {x, 0, (n/2)^(1/4)}, {y, x, (n-x^4)^(1/4)}, {z, 0, Sqrt[16(n-x^4-y^4)/23]}]; tab=Append[tab, r], {n, 0, 100}]; Print[tab]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A175372
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Number of integer pairs (x,y) satisfying x^4 + y^4 = n.
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+10
2
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1, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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G.f.: (1 + 2*Sum_{j>=1} x^(j^4))^2.
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MAPLE
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seq(coeff(series((1+2*add(x^(j^4), j=1..n))^2, x, n+1), x, n), n = 0 .. 120); # Muniru A Asiru, Oct 07 2018
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MATHEMATICA
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CoefficientList[Series[(1 + 2*Sum[x^(j^4), {j, 1, 100}])^2, {x, 0, 120}], x] (* G. C. Greubel, Oct 06 2018 *)
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PROG
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(PARI) x='x+O('x^120); Vec((1+2*sum(j=1, 50, x^(j^4)))^2) \\ G. C. Greubel, Oct 06 2018
(Magma) m:=120; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!((1+2*(&+[x^(j^4): j in [1..50]]))^2)); // G. C. Greubel, Oct 06 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A216280
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Number of nonnegative solutions to the equation x^4 + y^4 = n.
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+10
2
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1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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OFFSET
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1,635318657
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COMMENTS
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The first n with a(n) > 1 is 635318657 = 41 * 113 * 241 * 569, with a(635318657) = 2. Izadi, Khoshnam, & Nabardi show that for any n with a(n) > 1, the elliptic curve y^2 = x^3 - nx has rank at least 3. According to gp, y^2 = x^3 - 635318657x has analytic rank 4 (and first nonzero derivative around 35741.7839). - Charles R Greathouse IV, Jan 12 2017
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LINKS
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MATHEMATICA
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Reap[For[n = 1, n <= 1000, n++, r = Reduce[0 <= x <= y && x^4 + y^4 == n, {x, y}, Integers]; sols = Which[r === False, 0, r[[0]] == And, 1, r[[0]] == Or, Length[r], True, Print[n, " ", r]]; If[sols != 0, Print[n, " ", sols, " ", r]]; Sow[sols]]][[2, 1]] (* Jean-François Alcover, Feb 22 2019 *)
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PROG
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(PARI) a(n)=my(t=thue(thueinit('x^4+1, 1), n)); sum(i=1, #t, t[i][1]>=0 && t[i][2]>=t[i][1]) \\ Charles R Greathouse IV, Jan 12 2017
(PARI) first(n)=my(T=thueinit('x^4+1, 1), v=vector(n), t); for(k=1, n, t=thue(T, k); v[k]=sum(i=1, #t, t[i][1]>=0 && t[i][2]>=t[i][1])); v \\ Charles R Greathouse IV, Jan 12 2017
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CROSSREFS
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Cf. A004831 (positions of nonzero terms).
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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A247099
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Numbers which are the sum or difference of two fifth powers.
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+10
2
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0, 1, 2, 31, 32, 33, 64, 211, 242, 243, 244, 275, 486, 781, 992, 1023, 1024, 1025, 1056, 1267, 2048, 2101, 2882, 3093, 3124, 3125, 3126, 3157, 3368, 4149, 4651, 6250, 6752, 7533, 7744, 7775, 7776, 7777, 7808, 8019, 8800, 9031, 10901, 13682, 15552, 15783, 15961
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) << n^(5/2). Can this be improved?
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EXAMPLE
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31 = 2^5 - 1^5, 32 = 2^5 + 0^5, 33 = 2^5 + 1^5.
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MATHEMATICA
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Union[Flatten[{Total[#], Abs[#[[2]]-#[[1]]]}&/@Tuples[Range[0, 10]^5, 2]]] (* Harvey P. Dale, Mar 30 2015 *)
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PROG
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(PARI) T=thueinit('z^5+1);
is(n)=n==0 || #thue(T, n)>0
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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