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 A053903 #17 Oct 18 2024 14:36:40
%S A053903 1,16,1156,6561,111556,556516,6661561,11115556,165611161,1111155556,
%T A053903 1566655561,6661661161,111111555556,1551155666116,1561665111556,
%U A053903 11111115555556,156166661115556,1111111155555556,111111111555555556,5115511551651111556,11111111115555555556
%N A053903 Squares composed of digits {1,5,6}.
%C A053903 Includes all numbers of the form ((10^k-1)/3 + 1)^2. - _Andrew Howroyd_, Oct 18 2024
%H A053903 Zhao Hui Du, <a href="/A053903/b053903.txt">Table of n, a(n) for n = 1..55</a>
%H A053903 Patrick De Geest, <a href="http://www.worldofnumbers.com/threedigits.htm">Squares containing at most three distinct digits, Index entries for related sequences</a>
%F A053903 a(n) = A053902(n)^2. - _Andrew Howroyd_, Oct 18 2024
%Y A053903 Cf. A053902.
%K A053903 nonn,base
%O A053903 1,2
%A A053903 _Patrick De Geest_, Mar 15 2000