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 A119195 #7 Jul 13 2021 21:29:06
%S A119195 2,3,8,11,36,391,816,8563,39183,2594751,12436829803183
%N A119195 Numbers k such that the k-th triangular number contains only digits {3,6,7}.
%C A119195 Next term exceeds 1.4*10^16.
%H A119195 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr367.html">Tridigital Triangular Numbers</a>
%Y A119195 Cf. A000217, A119194. See A119034 for a table of cross-references.
%K A119195 nonn,base,more
%O A119195 1,1
%A A119195 _Giovanni Resta_, May 10 2006