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 A119233 #9 Jul 13 2021 21:31:25
%S A119233 3,11,36,36817576,365512507857054543
%N A119233 Numbers k such that the k-th triangular number contains only digits {6,7,9}.
%C A119233 Next term exceeds 4.4*10^17.
%H A119233 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr679.html">Tridigital Triangular Numbers</a>
%Y A119233 Cf. A000217, A119232. See A119034 for a table of cross-references.
%K A119233 nonn,base,more
%O A119233 1,1
%A A119233 _Giovanni Resta_, May 10 2006
%E A119233 365512507857054543 from _Max Alekseyev_, Mar 10 2009