A176902 Primes p such that p-1 and p+1 are both non-semiprime.

2, 17, 19, 29, 31, 41, 43, 53, 67, 71, 79, 89, 97, 101, 103, 109, 113, 127, 131, 137, 139, 149, 151, 163, 173, 181, 191, 197, 199, 211, 223, 229, 233, 239, 241, 251, 257, 269, 271, 281, 283, 293, 307, 311, 317, 331, 337, 349, 353, 367, 373, 379, 389, 401, 409

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 28 2010

Keywords

• nonn

Comments

2 together with A060254.

Examples

			a(1)=2 because 2-1=1=non-semiprime and 2+1=3=non-semiprime.
		

Formula

a(n+1)=A060254(n)=A167915(n+1).

Extensions

Corrected (233, 239 inserted, 279 and 289 replaced by 379 and 389) by R. J. Mathar, Aug 12 2010