A100742 Smallest prime p such that (p+prime(n))/2 is prime.

2, 3, 5, 3, 3, 13, 5, 3, 3, 5, 3, 37, 5, 3, 11, 5, 3, 13, 7, 3, 13, 3, 3, 5, 37, 5, 3, 11, 13, 5, 7, 3, 5, 3, 17, 7, 37, 3, 11, 5, 23, 13, 3, 13, 5, 3, 3, 3, 47, 73, 29, 23, 13, 3, 5, 11, 5, 3, 37, 17, 19, 5, 7, 3, 13, 17, 3, 61, 11, 13, 5, 3, 19, 13, 3, 3, 5, 61, 53, 13, 3, 37, 23, 13, 7, 3, 5

Offset: 1

Author

David Wasserman, Jan 03 2005

Keywords

• easy
• nonn
• less

Crossrefs

Cf. A084704.

Programs

PARI

a(n) = {if (n==1, return (2)); p = 3; while(! isprime((prime(n)+p)/2), p = nextprime(p+1)); return (p);} \\ Michel Marcus, Jun 16 2013