A289356 Least number k such that n^2 + n + k is prime.

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, 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, 1, 17, 17, 7, 1, 5, 11, 1, 3, 1, 5, 5, 7, 1, 5, 1, 1, 3, 1, 11, 17, 5, 11, 11

Offset

0,1

Comments

a(A002384(n)) = 1.

a(A027752(n)) = 3, for n > 2.

Links

Robert Israel, Table of n, a(n) for n = 0..10000

Formula

a(n) = A013632(A002378(n)). - Robert Israel, Jul 05 2017

Maple

seq(nextprime(n^2+n)-(n^2+n), n=0..100); # Robert Israel, Jul 05 2017

Mathematica

Table[k = 1; While[! PrimeQ[n^2 + n + k], k++]; k, {n, 0, 85}] (* Michael De Vlieger, Jul 04 2017 *)

Prog

(PARI) for(n=0, 85, k={my(k=1); while(!isprime(n^2+n+k), k++); k; }; print1(k", "))

Crossrefs

Cf. A002378, A002384, A013632, A027752, A182047 (resulting primes).

Sequence in context: A047140 A047150 A280489 * A269977 A238710 A262905

Adjacent sequences: A289353 A289354 A289355 * A289357 A289358 A289359

Keyword

nonn

Author

Gionata Neri, Jul 03 2017

Status

approved