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 A129211 #9 Jun 08 2021 02:23:38
%S A129211 1,2,4,10,20,68,110,164,220,340,610,772,820,1010,1210,1220,1510,2020,
%T A129211 2420,2530,2788,3020,3740,3860,5060,6710,7004,7370,8020,9020,9316,
%U A129211 11110,11810,13124,13420,13612,13940,14740,16610,19580,20740,20876,22220
%N A129211 Numbers k such that k^3 divides 3^(k^2) - 1.
%H A129211 Robert Price, <a href="/A129211/b129211.txt">Table of n, a(n) for n = 1..249</a>
%t A129211 k=1; Do[ p=Prime[k]; If[ IntegerQ[ (PowerMod[ p+1, n^2, n^3 ] - 1 )/n^3 ], Print[ {k, p, n} ]], {n,1,100000} ]
%t A129211 Join[{1}, Select[Range[3000000], PowerMod[3, #^2, #^3] == 1 &]] (* _Robert Price_, Mar 31 2020 *)
%Y A129211 Cf. A067945 (numbers k such that k divides 3^k-1).
%Y A129211 Cf. A127103 (numbers k such that k^2 divides 3^k-1).
%K A129211 nonn
%O A129211 1,2
%A A129211 _Alexander Adamchuk_, Apr 03 2007