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%I #26 Jun 13 2021 03:22:48
%S 1,2,4,5,3763,125714,167716,1803962,2895548,4031785,36226466,
%T 16207566916,103742264732,29000474325364,51053256144532,
%U 219291270961199,1611547934753332,5816826177630619
%N Numbers k such that 2^k == 12 (mod k).
%H Joe K. Crump, <a href="http://web.archive.org/web/20120104074313/http://www.immortaltheory.com/NumberTheory/2nmodn.htm">2^n mod n</a>
%H OEIS Wiki, <a href="/wiki/2^n mod n">2^n mod n</a>
%t m = 12; Join[Select[Range[m], Divisible[2^# - m, #] &],
%t Select[Range[m + 1, 10^6], PowerMod[2, #, #] == m &]] (* _Robert Price_, Oct 08 2018 *)
%Y Cf. A015910, A036236, A050259, A033981, A051447, A033982, A051446, A033983, A128121, A128122, A128123, A128125, A128126.
%K hard,more,nonn
%O 1,2
%A _Alexander Adamchuk_, Feb 15 2007
%E More terms from _Ryan Propper_, Mar 23 2007
%E 1, 2, 4 and 5 added by _N. J. A. Sloane_, Apr 23 2007
%E a(13)-a(15) from _Max Alekseyev_, May 19 2011
%E a(15) corrected, a(16)-a(18) added by _Max Alekseyev_, Oct 02 2016