A171255 Primes which are the average of two distinct Mersenne primes (A000668).

5, 17, 19, 67, 79, 4099, 4111, 4159, 65537, 65539, 65551, 65599, 262147, 266239, 1073741827, 1073741839, 1073807359, 309485009821345068724785151

Offset: 1

Author

M. F. Hasler, Mar 06 2010

Keywords

• nonn

Comments

The subsequence of primes in A171253, which equals A171254 minus its subsequence A000668.

Examples

			a(n) = A171253(n) for n=1,2,3, since all of these terms are prime. The term A171253(4) = 65 is the first element of A171252 to be composite, and therefore not included in the present sequence A171255.
		

Links

• Jonathan Vos Post, Sums of three Mersenne primes, and prime sums of three Mersenne primes, SeqFan list, Mar 5, 2010.

Crossrefs

Cf. A171252, A171254 (includes elements of A000668).

Programs

PARI

select(isprime, concat(vector(#A00668,i,vector(i-1,j,A00668[i]+A00668[j])))/2) /* having defined A00668 as vector with initial terms of A000668. In PARI version 2.4.2, the syntax select( concat(...), x->isprime(x)) must be used. */

Formula

A171255 = A171253 intersect A000040 = A171254 \ A000668.