20,1

Starting at n=20 just because there are some n<20 without solution like for n=19, for the least k (A082467) it start at 4 as no solution for n<4.

Pierre CAMI, Table of n, a(n) for n = 20..10000

(PARI) a(n) = {k=1; while(isprime(n-k)*isprime(n+k) == 0, k++); k++; while(isprime(n-k)*isprime(n+k) == 0, k++); k; } \\ Michel Marcus, Nov 10 2013

Cf. A082467.

Sequence in context: A272962 A137392 A307639 * A309656 A309657 A296615

Adjacent sequences: A231480 A231481 A231482 * A231484 A231485 A231486

nonn

Pierre CAMI, Nov 09 2013

approved