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 A119059 #9 Mar 22 2023 17:53:44
%S A119059 3,300,3003,3403,3444000,344334403,433430403,3434340003,4033034303403,
%T A119059 3430000044444403,4333004330434300,300034434334030003,
%U A119059 333343033034040030,44400033434030304430,3340004334430334340000,30340003004344033440000,4430044300033330340443003
%N A119059 Triangular numbers composed of digits {0,3,4}.
%H A119059 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr034.html">Tridigital Triangular Numbers</a>
%F A119059 a(n) = A000217(A119060(n)). - _Michel Marcus_, Mar 22 2023
%Y A119059 Cf. A000217, A058430, A119060. See A119033 for a table of cross-references.
%K A119059 nonn,base
%O A119059 1,1
%A A119059 _Giovanni Resta_, May 10 2006
%E A119059 a(16)-a(17) from _Tyler Busby_, Mar 22 2023