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 A119203 #7 Jul 13 2021 21:29:48
%S A119203 3,9,10,11,30,36,94,96,105,114,305,1043,2988,3303,3363,11363,3021769,
%T A119203 3054388,10627009,33330030,33330036,33336636,94302243,115470036,
%U A119203 305177471,336352955885,330353339515569,955663806624114
%N A119203 Numbers k such that the k-th triangular number contains only digits {4,5,6}.
%H A119203 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr456.html">Tridigital Triangular Numbers</a>
%Y A119203 Cf. A000217, A119202. See A119034 for a table of cross-references.
%K A119203 nonn,base
%O A119203 1,1
%A A119203 _Giovanni Resta_, May 10 2006