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A156585
Numbers such that (2^(n^2)-1)/(2^n-1) is prime.
4
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
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
KEYWORD
hard,more,nonn
AUTHOR
M. F. Hasler, Feb 10 2009
STATUS
approved