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%I #20 Jun 13 2021 03:22:52
%S 1,2,6,18,16666,262134,4048124214,24430928839,243293052886,
%T 41293676570106,3935632929857549
%N Numbers k such that 2^k == 10 (mod k).
%C Some larger terms: 266895924489780149, 2335291686841914329, 18494453435532853111
%H Joe K. Crump, <a href="https://web.archive.org/web/20120104074313/http://www.immortaltheory.com/NumberTheory/2nmodn.htm">2^n mod n</a>
%t m = 10; 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 (numbers k such that 2^k == 3 (mod k)), A033981, A051447, A033982, A051446, A033983, A128121, A128122, A128124, A128125, A128126.
%K hard,more,nonn
%O 1,2
%A _Alexander Adamchuk_, Feb 15 2007
%E 1, 2 and 6 added by _N. J. A. Sloane_, Apr 23 2007
%E Missing terms a(9)-a(10) added by _Max Alekseyev_, Dec 16 2013
%E a(11) from _Max Alekseyev_, Sep 27 2016