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%I #21 Mar 06 2020 00:16:18
%S 5,73,1082401,4432676798593,1298708349570020393652962442872833,
%T 91355004067076339167413824240109498970069278721,
%U 7588608256743087977590500540116743445925584618982806531428980886590618779326218241
%N a(n) = (2^p^2 - 1)/(2^p - 1) where p is the n-th prime.
%C 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
%F a(n) = A070526(prime(n)), a(n) = A019320(prime(n)^2). - _Thomas Ordowski_, Feb 18 2014
%t Table[Cyclotomic[Prime[n]^2, 2], {n, 7}] (* _Arkadiusz Wesolowski_, May 13 2012 *)
%t Table[(2^Prime[n]^2-1)/(2^Prime[n]-1),{n,10}] (* _Harvey P. Dale_, Apr 06 2019 *)
%Y Cf. A051154, A051155, A051157.
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_
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