%I #30 Sep 08 2022 08:45:30
%S 1,2,14,35,77,98,686,1715,5957,18995,26075,43921,49901,52334,86555,
%T 102475,221995,250355,1228283,1493597,4260059,6469715,10538675,
%U 15374219,19617187,22731275,53391779,60432239,68597795,85672139,175791077
%N Numbers k such that 2^k == 18 (mod k).
%H Joe Crump (joecr(AT)carolina.rr.com) <a href="/A128126/b128126.txt">Table of n, a(n) for n = 1..50</a>
%H Joe K. Crump, <a href="http://web.archive.org/web/20070614175509/http://www.immortaltheory.com/NumberTheory/2nmodn.htm">2^n mod n</a>
%t m = 18; Join[Select[Range[m], Divisible[2^# - m, #] &],
%t Select[Range[m + 1, 10^6], PowerMod[2, #, #] == m &]] (* _Robert Price_, Oct 08 2018 *)
%o (PARI) isok(n) = Mod(2, n)^n == 18; \\ _Michel Marcus_, Oct 09 2018
%o (Magma) [1,2,14] cat [n: n in [1..10^8] | Modexp(2, n, n) eq 18]; // _Vincenzo Librandi_, Apr 05 2019
%Y Cf. A015910, A036236, A050259 (numbers k such that 2^k == 3 (mod k)), A033981, A051447, A033982, A051446, A033983, A128121, A128122, A128123, A128124, A128125.
%K nonn
%O 1,2
%A _Alexander Adamchuk_, Feb 15 2007
%E More terms from Joe Crump (joecr(AT)carolina.rr.com), Mar 04 2007
%E 1, 2 and 14 added by _N. J. A. Sloane_, Apr 23 2007