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 A053880 #16 Aug 11 2024 14:41:32
%S A053880 1,2,11,12,21,38,338,1488,3338,11011,20521,33338,210771,333338,
%T A053880 3333338,14636332,15570521,20279162,33333338,45947921,49136668,
%U A053880 66641662,333333338,648940838,3333333338,6412661079,14632642079,33333333338
%N A053880 Numbers k such that k^2 contains only digits {1,2,4}.
%H A053880 Zhao Hui Du, <a href="/A053880/b053880.txt">Table of n, a(n) for n = 1..54</a>
%H A053880 Author?, <a href="http://web.archive.org/web/20080708203024/http://blue.kakiko.com/mmrmmr/htm/eqtn06.html">Source</a>(<a href="http://web.archive.org/web/20060426155831/http://blue.kakiko.com/mmrmmr/txt/eqtn06.txt">txt</a>)
%H A053880 P. De Geest, <a href="https://www.worldofnumbers.com/threedigits.htm">Squares containing at most three distinct digits, Index entries for related sequences</a>
%Y A053880 Cf. A053881.
%K A053880 nonn,base
%O A053880 1,2
%A A053880 _Patrick De Geest_, Mar 15 2000
%E A053880 More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 04 2005