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 A218389 #12 Jul 13 2021 07:23:51
%S A218389 8944,2209995667055,6957333458215,20001000974971249775
%N A218389 Numbers k such that the k-th triangular number contains only digits {0,2,4}.
%C A218389 No other terms below 1.4*10^20.
%H A218389 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr024.html">Tridigital Triangular Numbers</a>
%Y A218389 Cf. A000217, A218390. See A119034 for a table of cross-references.
%K A218389 base,nonn,more
%O A218389 1,1
%A A218389 _Max Alekseyev_, Oct 27 2012