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 A116639 #16 Oct 15 2016 09:46:51 %S A116639 1,2,14,22,1582,11266,52766,76202,100562,494371,641141,1698494, %T A116639 66593158,469296521,10917186079,12062558662,4928050067287, %U A116639 5315948729617,29841213777637,113215787397262,778590786358582,787324867879046 %N A116639 Numbers n such that 13^n == 15 (mod n). %C A116639 No other terms below 10^15. Some large terms: 6991413003775539262, 2360895769139218729155198091. - _Max Alekseyev_, Oct 15 2016 %t A116639 Select[Range[25000000],PowerMod[13,#,# ]==15&] (* _Harvey P. Dale_, Feb 03 2009 *) %Y A116639 Cf. A116609, A116611, A116620, A116621, A116622, A116629, A116630, A116631, A116632, A116636, A116638. %K A116639 nonn %O A116639 1,2 %A A116639 _Zak Seidov_, Feb 19 2006 %E A116639 One more term from _Harvey P. Dale_, Feb 03 2009 %E A116639 Edited by _Max Alekseyev_, Sep 19 2009 %E A116639 a(14)-a(22) from _Max Alekseyev_, May 04 2010, Apr 29 2014, Oct 15 2016