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 A119116 #8 Jul 13 2021 07:32:20
%S A119116 1,2,3,8,11,16,36,163,816,115166,475633,1151836,5677378,35585421,
%T A119116 35598136,51596833,258114833,1152095166,11060118546,112366468411,
%U A119116 1797838514253,11234888843541,78909614580621,1632858433307288
%N A119116 Numbers k such that the k-th triangular number contains only digits {1,3,6}.
%H A119116 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr136.html">Tridigital Triangular Numbers</a>
%Y A119116 Cf. A000217, A119115. See A119034 for a table of cross-references.
%K A119116 nonn,base
%O A119116 1,2
%A A119116 _Giovanni Resta_, May 10 2006