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 A015968 #27 Aug 28 2021 17:59:28 %S A015968 1,2,226,25538,2885794,326094722,36848703586,4163903505218, %T A015968 470521096089634,53168883858128642,638026606623638426, %U A015968 6008083875968536546,6789793858544278594 %N A015968 Positive integers k such that k | (15^k + 1). %C A015968 No other terms below 10^19. %C A015968 Some larger terms: 15878365178317113816706, (15^226+1)/238519527370488646998297200411598927857 (228 digits). - _Max Alekseyev_, Aug 03 2011 %Y A015968 Column k=15 of A333429. %K A015968 nonn,more %O A015968 1,2 %A A015968 _Robert G. Wilson v_ %E A015968 a(6)-a(13) from _Max Alekseyev_, Oct 02 2010, Aug 03 2011, Sep 17 2017