A156585 Numbers such that (2^(n^2)-1)/(2^n-1) is prime.

2, 3, 7, 59

Offset

1,1

Comments

It is easy to see that all terms of this sequence must be prime; this motivates the definition of A051156(n) = (2^prime(n)^2-1)/(2^prime(n)-1).

No further terms up to n=1999. - Andreas Höglund, Apr 06 2018

Links

Table of n, a(n) for n=1..4.

Mathematica

Select[Prime[Range[17]], PrimeQ[Cyclotomic[#^2, 2]] &] (* Arkadiusz Wesolowski, May 13 2012 *)

Prog

(PARI) for/*prime*/( n=1, 99, is/*pseudo*/prime( (2^n^2-1)/(2^n-1) ) & print1(n, ", "))

Crossrefs

Cf. A051156.

Sequence in context: A343557 A238399 A159611 * A354744 A299923 A337189

Adjacent sequences: A156582 A156583 A156584 * A156586 A156587 A156588

Keyword

hard,more,nonn

Author

M. F. Hasler, Feb 10 2009

Status

approved