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%I #23 Oct 08 2018 18:14:01
%S 1,13,481,44669,1237231339,1546675117,62823773963,284876771881,
%T 1119485807557,26598440989093
%N Integers n such that 2^n == 15 (mod n).
%C No other terms below 10^14.
%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 = 15; Join[Select[Range[m], Divisible[2^# - m, #] &],
%t Select[Range[m + 1, 10^3], PowerMod[2, #, #] == m &]] (* _Robert Price_, Oct 08 2018 *)
%Y Cf. A125000, A124974, A033982, A033981, A050259, A124977, A124965, A015911, A015910.
%Y Cf. A015910, A015911, A033981, A050259, A124965, A124974, A124977, A015910, A015911, A033982, A125000.
%K nonn,more
%O 1,2
%A Joe K. Crump (joecr(AT)carolina.rr.com)
%E One more term from Joe K. Crump (joecr(AT)carolina.rr.com), Jun 20 2000
%E Edited by _N. J. A. Sloane_, Jul 03 2008 at the suggestion of _R. J. Mathar_
%E Terms 1, 13 prepended by _Max Alekseyev_, May 18 2011
%E a(10) from _Max Alekseyev_, Dec 15 2013