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A051156
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a(n) = (2^p^2 - 1)/(2^p - 1) where p is the n-th prime.
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8
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5, 73, 1082401, 4432676798593, 1298708349570020393652962442872833, 91355004067076339167413824240109498970069278721, 7588608256743087977590500540116743445925584618982806531428980886590618779326218241
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OFFSET
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1,1
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COMMENTS
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Note that a(n) = Phi(p,2^p) or a(n) = Phi(p^2,2), where Phi(m,x) is the m-th cyclotomic polynomial and p is the n-th prime. - Thomas Ordowski, Feb 18 2014
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LINKS
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Table of n, a(n) for n=1..7.
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FORMULA
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a(n) = A070526(prime(n)), a(n) = A019320(prime(n)^2). - Thomas Ordowski, Feb 18 2014
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MATHEMATICA
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Table[Cyclotomic[Prime[n]^2, 2], {n, 7}] (* Arkadiusz Wesolowski, May 13 2012 *)
Table[(2^Prime[n]^2-1)/(2^Prime[n]-1), {n, 10}] (* Harvey P. Dale, Apr 06 2019 *)
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CROSSREFS
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Cf. A051154, A051155, A051157.
Sequence in context: A353042 A128889 A131958 * A092826 A334258 A322446
Adjacent sequences: A051153 A051154 A051155 * A051157 A051158 A051159
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane
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STATUS
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approved
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