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 A055695 #11 Jul 11 2021 13:09:21
%S A055695 2,6,30,146,42486,102966,597198,2847366,7998606,13133666,30478158,
%T A055695 67622310,74476206,101258190,105161166,106364286,187605438,230000550,
%U A055695 242915166,401913582,406756350,444314574,848205078,899715894,1508418054,1575220350,1578086334,1691859102
%N A055695 Numbers k such that 12^k == -1 (mod k-1).
%t A055695 Do[If[PowerMod[12, n, n-1]==n-2, Print[n]], {n, 2, 10^8}]
%K A055695 nonn
%O A055695 1,1
%A A055695 _Robert G. Wilson v_, Jun 09 2000
%E A055695 Terms a(14) onward from _Max Alekseyev_, Oct 12 2012