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

2, 3, 7, 59

Offset: 1

Author

M. F. Hasler, Feb 10 2009

Keywords

• hard
• more
• nonn

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

Crossrefs

Cf. A051156.

Programs

Mathematica

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

PARI

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