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 A058430 #15 Oct 27 2019 05:12:34
%S A058430 4,300304,343030433344,3433000433443344,40330334403443044,
%T A058430 33330430344333340030340440344044034304,
%U A058430 434003044400343443044430000434430333044043044
%N A058430 Squares composed of digits {0,3,4}, not ending with zero.
%H A058430 Patrick De Geest, <a href="http://www.worldofnumbers.com/threedigits.htm">Index to related sequences</a>
%H A058430 Hisanori Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/math02/math0210.htm#034">Sporadic tridigital solutions</a>
%F A058430 a(n) = A058429(n)^2. - _M. F. Hasler_, Aug 29 2012
%o A058430 (PARI) \\ see A058429 - _M. F. Hasler_, May 14 2007
%K A058430 nonn,base,hard
%O A058430 1,1
%A A058430 _Patrick De Geest_, Nov 15 2000
%E A058430 One more term from _M. F. Hasler_, May 14 2007
%E A058430 One more term from Mishima's page added by _Max Alekseyev_, Jul 13 2009