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A156585 Numbers such that (2^(n^2)-1)/(2^n-1) is prime. 3
2, 3, 7, 59 (list; graph; refs; listen; history; text; internal format)
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: A253574 A238399 A159611 * A299923 A087358 A255357

Adjacent sequences:  A156582 A156583 A156584 * A156586 A156587 A156588

KEYWORD

hard,more,nonn

AUTHOR

M. F. Hasler, Feb 10 2009

STATUS

approved

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Last modified September 20 09:11 EDT 2020. Contains 337264 sequences. (Running on oeis4.)