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Numbers n such that n = 4*(2*i+1)+1 and 2^(n-2) == 1 (mod (2*i+1)).
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%I #10 Aug 02 2015 13:25:19

%S 5,29,2045,40133,971837,5063357,7354397,16554917,17786525,42244637,

%T 52717277,79704029,84896957,153424637,262984997,288644957,328721213,

%U 350252957,353294757,393411197,498253253,613578149,634102757,876046277

%N Numbers n such that n = 4*(2*i+1)+1 and 2^(n-2) == 1 (mod (2*i+1)).

%H Max Alekseyev, <a href="/A175905/b175905.txt">Table of n, a(n) for n = 1..79</a>

%t fQ[n_] := PowerMod[2, 8n + 3, 2n + 1] == 1; k = 1; lst = {5}; While[k < 10^9/8, If[ fQ@k, AppendTo[lst, 8k + 5]; Print[8k + 5]]; k++ ] (* _Robert G. Wilson v_, Oct 20 2010 *)

%K nonn

%O 1,1

%A _Alzhekeyev Ascar M_, Oct 12 2010

%E a(13) onwards from _Robert G. Wilson v_, Oct 20 2010