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%I #15 Mar 30 2021 19:43:36
%S 1,7,13,19,31,37,49,55,61,67,85,91,109,121,127,139,157,175,181,193,
%T 199,211,217,235,247,265,289,301,307,313,319,325,337,379,391,397,409,
%U 415,445,451,469,487,499,517,535,541,571,577,589,595,631,667,679,685,691
%N Numbers k such that (k+2) divides 2^(k-1) - 1.
%C Is a(n)/(n*log(n)*log(log(n))) bounded?
%H Amiram Eldar, <a href="/A081765/b081765.txt">Table of n, a(n) for n = 1..10000</a>
%t Select[Range[1000], PowerMod[2, # - 1, # + 2] == 1 &] (* _Amiram Eldar_, Mar 30 2021 *)
%Y Cf. A000225.
%K easy,nonn
%O 1,2
%A _Benoit Cloitre_, Apr 09 2003
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