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 A055688 #18 Aug 13 2024 12:00:39
%S A055688 2,3,7,14,15,175,855,2695,78127,103974,106695,121975,420210,487375,
%T A055688 1299375,2174655,3895095,4151455,5842215,5951130,6508335,10637055,
%U A055688 20117895,24482958,31999695,32282054,32620203,32872455,34258455
%N A055688 Numbers k such that 5^k == -1 (mod k-1).
%H A055688 Amiram Eldar, <a href="/A055688/b055688.txt">Table of n, a(n) for n = 1..200</a>
%t A055688 Do[If[PowerMod[5, n, n-1]==n-2, Print[n]], {n, 2, 10^8}]
%t A055688 Select[Range[2,35*10^6],PowerMod[5,#,#-1]==#-2&] (* _Harvey P. Dale_, Aug 13 2024 *)
%Y A055688 Cf. A055685, A055686, A055687, A055689, A055690, A055691, A055692, A055693, A055694, A055695.
%K A055688 nonn
%O A055688 1,1
%A A055688 _Robert G. Wilson v_, Jun 09 2000
%E A055688 a(22) corrected by _Amiram Eldar_, Jul 23 2021