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 A119212 #13 Mar 28 2023 14:49:49
%S A119212 6,66,666,8646,84666,886446,88864446,646686666,6488484486,8888644446,
%T A119212 888886444446,88888864444446,8888888644444446,888888886444444446,
%U A119212 88888888864444444446,484888446864684484446,8888888888644444444446,888888888886444444444446
%N A119212 Triangular numbers composed of digits {4,6,8}.
%H A119212 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr468.html">Tridigital Triangular Numbers</a>.
%F A119212 a(n) = A000217(A119213(n)). - _Michel Marcus_, Mar 27 2023
%Y A119212 Cf. A000217, A053959, A119213. See A119033 for a table of cross-references.
%K A119212 nonn,base
%O A119212 1,1
%A A119212 _Giovanni Resta_, May 10 2006
%E A119212 a(18) from _Tyler Busby_, Mar 28 2023