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 A119184 #9 Mar 15 2023 18:31:30
%S A119184 3,6,36,66,666,333336,3664664466,66336663646,3343646334464646,
%T A119184 334446636363634446,346644344666643436,3644434346644436366346,
%U A119184 4446663663333436343436,664333446446364463633446,436633343363366333434433646,6336363664446634343634443466
%N A119184 Triangular numbers composed of digits {3,4,6}.
%H A119184 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr346.html">Tridigital Triangular Numbers</a>
%F A119184 a(n) = A000217(A119185(n)). - _Michel Marcus_, Mar 15 2023
%Y A119184 Cf. A000217, A053939, A119185. See A119033 for a table of cross-references.
%K A119184 nonn,base
%O A119184 1,1
%A A119184 _Giovanni Resta_, May 10 2006
%E A119184 a(15)-a(16) from _Tyler Busby_, Mar 15 2023