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 A119126 #8 Jul 13 2021 07:28:12
%S A119126 1,3,11,36,113,288,541,963,1711,2868,5313,36458,48258,182463,288588,
%T A119126 363633,536956,568588,1711411,2988113,9425088,11055868,30533313,
%U A119126 47257686,48200963,963446588,1527359886,1825604911,363633363333
%N A119126 Numbers k such that the k-th triangular number contains only digits {1,4,6}.
%H A119126 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr146.html">Tridigital Triangular Numbers</a>
%Y A119126 Cf. A000217, A119125. See A119034 for a table of cross-references.
%K A119126 nonn,base
%O A119126 1,2
%A A119126 _Giovanni Resta_, May 10 2006