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 A119159 #12 Jul 13 2021 07:25:56
%S A119159 9,10,225,714,6714,22114,2119209,2211449,102523609,942573334,
%T A119159 95336514049,3333030289167658390
%N A119159 Numbers k such that the k-th triangular number contains only digits {2,4,5}.
%C A119159 Next term exceeds 1.4*10^20.
%H A119159 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr245.html">Tridigital Triangular Numbers</a>
%Y A119159 Cf. A000217, A119158. See A119034 for a table of cross-references.
%K A119159 nonn,base,more
%O A119159 1,1
%A A119159 _Giovanni Resta_, May 10 2006
%E A119159 a(12) from _Max Alekseyev_, Aug 19 2013