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 A053923 #18 Oct 18 2024 14:36:32
%S A053923 4,64,4624,26244,446224,26646244,44462224,662444644,4444622224,
%T A053923 6266622244,26646644644,444446222224,44444462222224,64664242622464,
%U A053923 624666644462224,4444444622222224,444444446222222224,44444444462222222224,64266662664264424464,4444444444622222222224
%N A053923 Squares composed of digits {2,4,6}.
%C A053923 Includes all numbers of the form (2*(10^k-1)/3 + 2)^2 for k >= 1. - _Andrew Howroyd_, Oct 18 2024
%H A053923 Zhao Hui Du, <a href="/A053923/b053923.txt">Table of n, a(n) for n = 1..47</a>
%H A053923 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 A053923 a(n) = A053922(n)^2. - _Andrew Howroyd_, Oct 18 2024
%t A053923 Table[Select[FromDigits/@Tuples[{2,4,6},n],IntegerQ[Sqrt[#]]&],{n,10}]//Flatten (* The program generates the first 10 terms of the sequence.
%t A053923 To generate more, increase the "n" constant but the program may take a long time to run. *) (* _Harvey P. Dale_, Sep 25 2021 *)
%Y A053923 Cf. A053922.
%K A053923 nonn,base
%O A053923 1,1
%A A053923 _Patrick De Geest_, Mar 15 2000