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 A030174 #21 Jul 17 2025 14:49:21
%S A030174 1,121,12321,1322122321,132233322321,213223221121,13223121322321,
%T A030174 1212111311221321,131332121232312121,31121322221111133211321,
%U A030174 3322133322121313132333322321,12232213113321121113332133323121,3231221313313311221231322223122312333121,311323333121312322332133323111223321313321
%N A030174 Squares composed of digits {1,2,3}.
%H A030174 Patrick De Geest, <a href="https://www.worldofnumbers.com/threedigits.htm">Squares containing at most three distinct digits, Index entries for related sequences</a>.
%H A030174 Hisanori Mishima, <a href="https://www.asahi-net.or.jp/~KC2H-MSM/mathland/math02/math0210.htm#123">Sporadic tridigital solutions</a>.
%H A030174 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SquareNumber.html">Square Number</a>.
%H A030174 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>)
%F A030174 a(n) = A030175(n)^2. - _Elmo R. Oliveira_, Jul 17 2025
%Y A030174 Cf. A030175.
%K A030174 nonn,base
%O A030174 1,2
%A A030174 _Patrick De Geest_
%E A030174 More terms from _Patrick De Geest_, Mar 15 2000.
%E A030174 More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 14 2005
%E A030174 a(13)-a(14) from Mishima's website added by _Elmo R. Oliveira_, Jul 17 2025