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 A119082 #8 Jul 13 2021 01:25:32
%S A119082 10,100,124,375,1000,10000,100000,1000000,3924474,10000000,100000000,
%T A119082 387492084,1000000000,3885885999,10000000000,31804089540,39371996915,
%U A119082 100000000000,122929061474,1000000000000,10000000000000
%N A119082 Numbers k such that the k-th triangular number contains only digits {0,5,7}.
%H A119082 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr057.html">Tridigital Triangular Numbers</a>
%Y A119082 Cf. A000217, A119081. See A119034 for a table of cross-references.
%K A119082 nonn,base
%O A119082 1,1
%A A119082 _Giovanni Resta_, May 10 2006