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 A055692 #18 Jul 12 2021 03:01:18
%S A055692 2,3,11,42,147,13818,21450,27594,41370,55011,126291,265722,417123,
%T A055692 1315635,3994571,5704611,6860490,9298842,13941354,14349027,17658578,
%U A055692 20382810,26557874,27841338,69831363,86550090,113272170,130457571,163013235,192688650,211142538,333792522
%N A055692 Numbers k such that 9^k == -1 (mod k-1).
%t A055692 Do[If[PowerMod[9, n, n-1]==n-2, Print[n]], {n, 2, 10^8}]
%o A055692 (PARI) isok(k) = Mod(9, k-1)^k == -1; \\ _Michel Marcus_, Jul 12 2021
%Y A055692 Cf. A001019.
%K A055692 nonn
%O A055692 1,1
%A A055692 _Robert G. Wilson v_, Jun 09 2000