This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A033983 #23 Oct 08 2018 18:14:01 %S A033983 1,13,481,44669,1237231339,1546675117,62823773963,284876771881, %T A033983 1119485807557,26598440989093 %N A033983 Integers n such that 2^n == 15 (mod n). %C A033983 No other terms below 10^14. %H A033983 Joe K. Crump, <a href="http://web.archive.org/web/20120104074313/http://www.immortaltheory.com/NumberTheory/2nmodn.htm">2^n mod n</a> %H A033983 OEIS Wiki, <a href="/wiki/2^n mod n">2^n mod n</a> %t A033983 m = 15; Join[Select[Range[m], Divisible[2^# - m, #] &], %t A033983 Select[Range[m + 1, 10^3], PowerMod[2, #, #] == m &]] (* _Robert Price_, Oct 08 2018 *) %Y A033983 Cf. A125000, A124974, A033982, A033981, A050259, A124977, A124965, A015911, A015910. %Y A033983 Cf. A015910, A015911, A033981, A050259, A124965, A124974, A124977, A015910, A015911, A033982, A125000. %K A033983 nonn,more %O A033983 1,2 %A A033983 Joe K. Crump (joecr(AT)carolina.rr.com) %E A033983 One more term from Joe K. Crump (joecr(AT)carolina.rr.com), Jun 20 2000 %E A033983 Edited by _N. J. A. Sloane_, Jul 03 2008 at the suggestion of _R. J. Mathar_ %E A033983 Terms 1, 13 prepended by _Max Alekseyev_, May 18 2011 %E A033983 a(10) from _Max Alekseyev_, Dec 15 2013