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 A218398 #11 Jul 13 2021 07:23:36
%S A218398 374184,7385400,203569507673559,6663335616682084400
%N A218398 Numbers k such that the k-th triangular number contains only digits {0,2,7}.
%C A218398 No other terms below 1.4*10^20.
%H A218398 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr027.html">Tridigital Triangular Numbers</a>
%Y A218398 Cf. A000217, A218397. See A119034 for a table of cross-references.
%K A218398 base,nonn,more
%O A218398 1,1
%A A218398 _Max Alekseyev_, Oct 28 2012