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 A053893 #18 Jul 16 2025 10:12:36
%S A053893 1,16,36,361,3136,136161,633616,1313316,1336336,13366336,66113161,
%T A053893 363131136,1616361616,6661661161,66631613161,31633661633161,
%U A053893 613163131661161,131616316361116161,1166361161363316361,136113161636611666116,316661133333361663161316,11136331666361661633111616
%N A053893 Squares composed of digits {1,3,6}.
%H A053893 Zhao Hui Du, <a href="/A053893/b053893.txt">Table of n, a(n) for n = 1..25</a>
%H A053893 Patrick De Geest, <a href="http://www.worldofnumbers.com/threedigits.htm">Squares containing at most three distinct digits, Index entries for related sequences</a>.
%H A053893 Hisanori Mishima, <a href="https://www.asahi-net.or.jp/~KC2H-MSM/mathland/math02/math0210.htm#136">Sporadic tridigital solutions</a>.
%F A053893 a(n) = A053892(n)^2. - _Elmo R. Oliveira_, Jul 16 2025
%t A053893 Select[Flatten[Table[FromDigits/@Tuples[{1,3,6},n],{n,20}]],IntegerQ[ Sqrt[ #]]&] (* _Harvey P. Dale_, Jul 20 2021 *)
%Y A053893 Cf. A053892.
%K A053893 nonn,base
%O A053893 1,2
%A A053893 _Patrick De Geest_, Mar 15 2000
%E A053893 More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 04 2005