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 A053909 #16 Oct 18 2024 14:36:36
%S A053909 1,16,81,1681,11881,1666681,818188816,6168688681,6661661161,
%T A053909 611686666816,1111166866161,11168168618161,18886681666161,
%U A053909 666868181611681,866686868686116,16668111611611681,668881818661618116,866881188818186116,6181118111681186116,6811866166886681616
%N A053909 Squares composed of digits {1,6,8}.
%H A053909 Andrew Howroyd, <a href="/A053909/b053909.txt">Table of n, a(n) for n = 1..27</a>
%H A053909 P. De Geest, <a href="https://www.worldofnumbers.com/threedigits.htm">Squares containing at most three distinct digits, Index entries for related sequences</a>
%F A053909 a(n) = A053908(n)^2. - _Andrew Howroyd_, Oct 18 2024
%t A053909 Flatten[Table[Select[FromDigits/@Tuples[{1,6,8},{n}], IntegerQ[Sqrt[#]]&],{n,10}]] (* _Harvey P. Dale_, Apr 22 2011 *)
%Y A053909 Cf. A053908.
%K A053909 nonn,base
%O A053909 1,2
%A A053909 _Patrick De Geest_, Mar 15 2000
%E A053909 a(18) onwards using A053908 added by _Andrew Howroyd_, Oct 18 2024