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 A071129 #5 Aug 01 2018 10:28:07
%S A071129 4,121,841,6889,60025,62001,68644,534361,540225,1042441,4791721,
%T A071129 4809249,20811844,43072969,43125489,43283241,387499225,387656721,
%U A071129 388129401,567725929,713584369,1255284900,2231617600,3487020601,3487493025,3488910489,31381768201
%N A071129 Squares which repeat with at least two full periods when written in base 3.
%H A071129 Giovanni Resta, <a href="/A071129/b071129.txt">Table of n, a(n) for n = 1..131</a> (terms < 3^45)
%e A071129 11^2 = 121 = 1|1|1|1|1 in base 3.
%e A071129 249^2 = 62001 = 1001|1001|100 in base 3.
%t A071129 psq[b_, nd_] := Block[{sq={}, r, x}, Do[r = Mod[nd, p]; Do[x = (b^( Floor[nd/p] p) - 1)/(b^p - 1) t b^r + Floor[t/b^(p - r)]; If[ IntegerQ@ Sqrt@ x, AppendTo[ sq, x]], {t, b^(p - 1), b^p - 1}], {p, nd/2}]; sq]; Union @@ (psq[3, #] & /@ Range[20]) (* _Giovanni Resta_, Aug 01 2018 *)
%Y A071129 Cf. A071128 (base 2) - A071135 (base 9), A069919 (base 10).
%K A071129 base,nonn
%O A071129 1,1
%A A071129 _Erich Friedman_, May 28 2002
%E A071129 a(25)-a(27) from _Giovanni Resta_, Aug 01 2018