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 A119094 #8 Jul 13 2021 01:24:24
%S A119094 12,39,132,1332,13332,41732,118387,126560,133332,1241612,1333332,
%T A119094 11905535,13333332,124970227,133333332,1333333332,11906972812,
%U A119094 13333333332,37418660507,37626774267,42163256012,133333333332
%N A119094 Numbers k such that the k-th triangular number contains only digits {0,7,8}.
%H A119094 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr078.html">Tridigital Triangular Numbers</a>
%Y A119094 Cf. A000217, A119093. See A119034 for a table of cross-references.
%K A119094 nonn,base
%O A119094 1,1
%A A119094 _Giovanni Resta_, May 10 2006