OFFSET
1,1
COMMENTS
The conjecture in A266152 implies that a(n) > 0 for all n > 0.
It seems that a(n) < n*(n+4)/2 for all n > 1.
LINKS
Zhi-Wei Sun, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1) = 3 since -1 = 1^4 - 3^3 + 5^2.
a(2) = 3 since -2 = 2^4 - 3^3 + 3^2.
a(11) = 28 since -11 = 5^4 - 28^3 + 146^2.
a(20) = 238 since -20 = 32^4 - 238^3 + 3526^2.
MATHEMATICA
SQ[n_]:=SQ[n]=n>0&&IntegerQ[Sqrt[n]]
Do[y=Floor[n^(1/3)]+1; Label[bb]; Do[If[SQ[-n+y^3-x^4], Print[n, " ", y]; Goto[aa]], {x, 1, (-n+y^3)^(1/4)}]; y=y+1; Goto[bb]; Label[aa]; Continue, {n, 1, 70}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Dec 22 2015
STATUS
approved