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 A119124 #8 Jul 13 2021 07:28:09
%S A119124 1,5,9,10,101,298,301,1761,10113,10114,15133,91010,297134,3329010,
%T A119124 10406301,15133698,30180826,47989885,101434130,301468258,942805541,
%U A119124 9544151561,16977369885,95335633898
%N A119124 Numbers k such that the k-th triangular number contains only digits {1,4,5}.
%C A119124 Next term exceeds 1.4*10^16.
%H A119124 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr145.html">Tridigital Triangular Numbers</a>
%Y A119124 Cf. A000217, A119123. See A119034 for a table of cross-references.
%K A119124 nonn,base,more
%O A119124 1,2
%A A119124 _Giovanni Resta_, May 10 2006