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 A119080 #8 Jul 13 2021 01:25:28
%S A119080 3,10,11,36,100,105,114,363,1000,1095,1100,3363,10000,11000,100000,
%T A119080 110000,1000000,1100000,10000000,11000000,11541720,33166430,33336636,
%U A119080 100000000,110000000,1000000000,1100000000,3363197899,3464103363
%N A119080 Numbers k such that the k-th triangular number contains only digits {0,5,6}.
%H A119080 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr056.html">Tridigital Triangular Numbers</a>
%Y A119080 Cf. A000217, A119079. See A119034 for a table of cross-references.
%K A119080 nonn,base
%O A119080 1,1
%A A119080 _Giovanni Resta_, May 10 2006