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 A119145 #8 Jul 13 2021 07:26:35
%S A119145 1,3,11,13,36,1386,1411,1543,438433,445241,5685366,19849388,36385963,
%T A119145 154671711,199808366,1408518133,3497461911,184180138433,1350308625456,
%U A119145 4892835517288,11505747426366,118253893522536,447137831091711
%N A119145 Numbers k such that the k-th triangular number contains only digits {1,6,9}.
%H A119145 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr169.html">Tridigital Triangular Numbers</a>
%Y A119145 Cf. A000217, A119144. See A119034 for a table of cross-references.
%K A119145 nonn,base
%O A119145 1,2
%A A119145 _Giovanni Resta_, May 10 2006