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%I #12 Feb 09 2021 01:56:21
%S 28,292,553,5026,7519,20062,50888,57337,126532,337372,518161,555448,
%T 757156,811687,849583,1518076,3623809,4529623,6752431,6908068,6909961,
%U 7826888,9568183,13594936,16113217,20766748,21596722,28534984,34462456
%N Numbers k such that 2^(k(k-1)) == 8 (mod k).
%C Related to A127931.
%C Up to 10^9, there are 55 terms (21 odd and 34 even numbers). All except two, 50888 and 7826888, are congruent to 1 mod 3 and none are congruent to 0 mod 3. Is the sequence infinite?
%C Terms so far are == {1, 4, 7, 8, 10} (mod 12) or {1, 4, 7, 8, 13, 16, 19, 22, 28} (mod 30) and none are == +-3 (mod 8) nor == 5 (mod 10). - _Robert G. Wilson v_, Feb 12 2007
%H Zak Seidov and Robert G. Wilson v, <a href="/A126662/b126662.txt">Table of n, a(n) for n = 1..68</a>
%t lst = {}; n = 3; While[n < 10000000000, If[PowerMod[2, n(n - 1), n] == 8, AppendTo[lst, n]; Print@n]; n++ ]; lst (* _Robert G. Wilson v_, Feb 11 2007 *)
%Y Cf. A127931.
%K nonn
%O 1,1
%A _Zak Seidov_, Feb 10 2007
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