A176897 Primes p such that (p+1)/2 is not a prime.

2, 7, 11, 17, 19, 23, 29, 31, 41, 43, 47, 53, 59, 67, 71, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 163, 167, 173, 179, 181, 191, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 281, 283, 293, 307, 311, 317, 331

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 28 2010

Keywords

• nonn

Comments

Primes not in A005383. 2 together with A034849.

The Ramanujan primes, A104272, are a subsequence.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A005383, A034849, A104272.

Programs

Mathematica

Select[Prime[Range[100]], ! PrimeQ[(#+1)/2] &]

PARI

is(p) = isprime(p) && (p == 2 || !isprime((p+1)/2)); \\ Amiram Eldar, Jan 16 2025

Extensions

Entries checked by R. J. Mathar, May 01 2010