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A253911
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Concatenation of n-th nonprime and n-th prime.
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2
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12, 43, 65, 87, 911, 1013, 1217, 1419, 1523, 1629, 1831, 2037, 2141, 2243, 2447, 2553, 2659, 2761, 2867, 3071, 3273, 3379, 3483, 3589, 3697, 38101, 39103, 40107, 42109, 44113, 45127, 46131, 48137, 49139, 50149, 51151, 52157, 54163, 55167, 56173, 57179, 58181, 60191, 62193, 63197, 64199, 65211, 66223, 68227, 69229
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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a(5) = 911 because the 5th nonprime is 9 and the 5th prime is 11.
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MATHEMATICA
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cncat[{a_, b_}]:=FromDigits[Flatten[IntegerDigits/@{a, b}]]; Module[ {nn=100, np, len}, np = Select[Range[nn], !PrimeQ[#]&]; len=Length[np]; cncat/@Thread[{np, Prime[Range[len]]}]] (* Harvey P. Dale, Oct 17 2020 *)
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PROG
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(PARI) nprime(n)=c=0; k=1; while(k, if(!isprime(k), c++); if(c==n, return(k)); k++)
vector(50, n, eval(concat(Str(nprime(n)), Str(prime(n))))) \\ Derek Orr, Feb 06 2015
(Haskell)
import Data.Function (on)
a253911 n = a253911_list !! (n-1)
a253911_list = map read $
zipWith ((++) `on` show) a018252_list a000040_list :: [Integer]
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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