A171255 - OEIS

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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

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OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..18.

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

FORMULA

A171255 = A171253 intersect A000040 = A171254 \ A000668.

EXAMPLE

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.

PROG

(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. */

CROSSREFS

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

Sequence in context: A153320 A171253 A226623 * A304540 A306125 A255901

Adjacent sequences: A171252 A171253 A171254 * A171256 A171257 A171258

KEYWORD

nonn

AUTHOR

M. F. Hasler, Mar 06 2010

STATUS

approved