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A156585
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Numbers such that (2^(n^2)-1)/(2^n-1) is prime.
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4
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OFFSET
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1,1
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COMMENTS
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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
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LINKS
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Table of n, a(n) for n=1..4.
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MATHEMATICA
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Select[Prime[Range[17]], PrimeQ[Cyclotomic[#^2, 2]] &] (* Arkadiusz Wesolowski, May 13 2012 *)
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PROG
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(PARI) for/*prime*/( n=1, 99, is/*pseudo*/prime( (2^n^2-1)/(2^n-1) ) & print1(n, ", "))
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CROSSREFS
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Cf. A051156.
Sequence in context: A343557 A238399 A159611 * A354744 A299923 A337189
Adjacent sequences: A156582 A156583 A156584 * A156586 A156587 A156588
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KEYWORD
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hard,more,nonn
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AUTHOR
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M. F. Hasler, Feb 10 2009
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STATUS
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approved
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