A269485 - OEIS

%I #36 Mar 02 2016 10:17:54

%S 1,1,1,1,7,11,7,13,17,31,13,1,47,17,19,19,23,73,43,29,47,31,43,29,31,

%T 37,167,1,29,43,79,229,89,71,137,37,53,1,79,131,137,1,71,83,89,89,53,

%U 97,53,101,59,173,79,71,353,191,103,523,229,191,103,401,67,257

%N Least k > 0 such that n! + k^2 is prime.

%C a(n) = A033932(n) = 1 for n in A002981.

%H Jean-Marc Rebert, <a href="/A269485/b269485.txt">Table of n, a(n) for n = 0..500</a>

%e a(4) = 7, because 4! + 7^2 = 73 is prime and for 0 < i < 7, 4! + i^2 is not prime.

%t Table[SelectFirst[Range@ 10000, PrimeQ[n! + #^2] &], {n, 120}]

%t (* Version 10, or *)

%t Table[k = 1; While[! PrimeQ[n! + k^2], k++]; k, {n, 120}] (* _Michael De Vlieger_, Feb 28 2016 *)

%o (PARI) a(n) = {my(k=1); while (!isprime(n! + k^2), k++); k;} \\ _Michel Marcus_, Feb 29 2016

%Y Cf. A002981, A033932, A038202.

%K nonn

%O 0,5

%A _Jean-Marc Rebert_, Feb 28 2016