A231483 Smallest k > A082467(n) such that n-k and n+k are both prime.

9, 8, 15, 18, 7, 12, 15, 10, 15, 18, 7, 28, 15, 10, 27, 12, 7, 24, 15, 8, 21, 18, 5, 30, 15, 8, 27, 24, 11, 18, 9, 10, 15, 30, 13, 18, 15, 10, 21, 30, 7, 42, 21, 10, 33, 18, 7, 30, 21, 10, 9, 18, 11, 30, 27, 8, 33, 24, 11, 48, 21, 8, 21, 30

Offset: 20

Author

Pierre CAMI, Nov 09 2013

Keywords

• nonn

Comments

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.

Links

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

Crossrefs

Cf. A082467.

Programs

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