A171253 Semi-sums (average) of any two distinct Mersenne primes (A000668).

5, 17, 19, 65, 67, 79, 4097, 4099, 4111, 4159, 65537, 65539, 65551, 65599, 69631, 262145, 262147, 262159, 262207, 266239, 327679, 1073741825, 1073741827, 1073741839, 1073741887, 1073745919, 1073807359, 1074003967

Offset: 1

Author

M. F. Hasler, Mar 06 2010

Keywords

• nonn

Comments

Subsequence of A171252, excluding the terms of A000668 itself.

Examples

			a(1) = (A000668(2)+A000668(1))/2, a(2) = (A000668(3)+A000668(1))/2, a(3) = (A000668(3)+A000668(2))/2, a(4) = (A000668(4)+A000668(1))/2, ,...
		

Links

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

Crossrefs

Cf. A171252 (includes terms of A000668), A171255 (primes in this sequence).

Programs

PARI

concat(vector(#A000668,i,vector(i-1,j,A000668[i]+A000668[j])))/2 /* having defined A000668 as vector with initial terms of A000668 */

Formula

a(n) = A171252(A014132(n)).

A171253 = A171252 \ A000688.