

A268692


Numbers n such that 2^(n1)*(2^n  1) + 1 is prime (see A134169).


0



1, 2, 3, 6, 9, 10, 13, 19, 45, 46, 58, 141, 271, 336, 562, 601, 1128, 1635, 2718, 2920, 3933, 4351, 4729, 6556, 8349, 10851, 32641, 34039, 41050
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OFFSET

1,2


COMMENTS

The intersection of this sequence with A000043 gives 2, 3, 13, 19, ... which are the indices corresponding to primes just next to perfect numbers (A000396), see A061644.
There are prime members of this sequence (271, 601, 4729, ...) which are not in A000043.
a(30) > 50000. All the primes corresponding to terms up to a(29) have been certified by the PFGW software performing the BrillhartLehmerSelfridge N1 test.  Giovanni Resta, Apr 11 2016


LINKS

Table of n, a(n) for n=1..29.


PROG

(PARI) for(n=0, 10^5, ispseudoprime(2^(n1)*(2^n1)+1) && print1(n, ", "))


CROSSREFS

Cf. A134169, A061644, A000043, A000396, A006516.
Sequence in context: A190674 A188399 A047284 * A089160 A214974 A286434
Adjacent sequences: A268689 A268690 A268691 * A268693 A268694 A268695


KEYWORD

nonn,more


AUTHOR

Jeppe Stig Nielsen, Feb 11 2016


EXTENSIONS

a(27)a(29) from Giovanni Resta, Apr 11 2016


STATUS

approved



