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 A119187 #7 Jul 13 2021 21:04:33
%S A119187 2,3,8,10,11,36,85,103,105,114,816,2696,3363,8430,10617,10645,11257,
%T A119187 36211,327210,333657,1032989,1054071,3647836,33336636,265918617,
%U A119187 36148757471,259095941942,326605681382,1063536896742,3333666251008
%N A119187 Numbers k such that the k-th triangular number contains only digits {3,5,6}.
%H A119187 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr356.html">Tridigital Triangular Numbers</a>
%Y A119187 Cf. A000217, A119186. See A119034 for a table of cross-references.
%K A119187 nonn,base
%O A119187 1,1
%A A119187 _Giovanni Resta_, May 10 2006