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 A119196 #13 Mar 27 2023 07:39:07
%S A119196 3,6,36,66,666,333336,8868366,86638866,83838368386,636633688636,
%T A119196 3336366833866,3866366838336666,63386366836686666,
%U A119196 636638868363883336386,3868888666888666363866,66886368686886866888888866,683686666688383838366383386
%N A119196 Triangular numbers composed of digits {3,6,8}.
%C A119196 a(18) > 10^40. - _Tyler Busby_, Mar 24 2023
%H A119196 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr368.html">Tridigital Triangular Numbers</a>.
%F A119196 a(n) = A000217(A119197(n)). - _Tyler Busby_, Mar 24 2023
%Y A119196 Cf. A000217, A058466, A119197. See A119033 for a table of cross-references.
%K A119196 nonn,base
%O A119196 1,1
%A A119196 _Giovanni Resta_, May 10 2006
%E A119196 a(16)-a(17) from _Tyler Busby_, Mar 24 2023