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 A119062 #8 Jul 13 2021 01:20:34
%S A119062 2,10,24,77,100,1000,10000,100000,257100,1000000,2647829,10000000,
%T A119062 10349399,26657100,100000000,316340024,775313489,1000000000,
%U A119062 10000000000,100000000000,1000000000000,1003347948924,8403017712114
%N A119062 Numbers k such that the k-th triangular number contains only digits {0,3,5}.
%H A119062 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr035.html">Tridigital Triangular Numbers</a>
%Y A119062 Cf. A000217, A119061. See A119034 for a table of cross-references.
%K A119062 nonn,base
%O A119062 1,1
%A A119062 _Giovanni Resta_, May 10 2006