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%I #14 Jul 05 2017 02:54:08
%S 2,1,1,1,3,1,1,3,1,7,3,5,1,9,1,1,5,1,5,3,1,1,3,5,1,3,7,1,9,7,7,5,5,1,
%T 3,17,29,3,1,7,17,1,5,9,7,11,17,11,5,9,1,5,11,17,1,3,11,1,11,1,11,11,
%U 1,17,17,7,1,5,11,1,3,1,5,5,7,1,5,1,1,3,1,11,17,5,11,11
%N Least number k such that n^2 + n + k is prime.
%C a(A002384(n)) = 1.
%C a(A027752(n)) = 3, for n > 2.
%H Robert Israel, <a href="/A289356/b289356.txt">Table of n, a(n) for n = 0..10000</a>
%F a(n) = A013632(A002378(n)). - _Robert Israel_, Jul 05 2017
%p seq(nextprime(n^2+n)-(n^2+n), n=0..100); # _Robert Israel_, Jul 05 2017
%t Table[k = 1; While[! PrimeQ[n^2 + n + k], k++]; k, {n, 0, 85}] (* _Michael De Vlieger_, Jul 04 2017 *)
%o (PARI) for(n=0,85,k={my(k=1);while(!isprime(n^2+n+k),k++);k;};print1(k", "))
%Y Cf. A002378, A002384, A013632, A027752, A182047 (resulting primes).
%K nonn
%O 0,1
%A _Gionata Neri_, Jul 03 2017