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 A119211 #7 Jul 13 2021 21:30:28
%S A119211 3,11,36,976,1236,3048,964131,36536961224668,123828734689848,
%T A119211 299247973315331
%N A119211 Numbers k such that the k-th triangular number contains only digits {4,6,7}.
%C A119211 Next term exceeds 1.4*10^16.
%H A119211 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr467.html">Tridigital Triangular Numbers</a>
%Y A119211 Cf. A000217, A119210. See A119034 for a table of cross-references.
%K A119211 nonn,base,more
%O A119211 1,1
%A A119211 _Giovanni Resta_, May 10 2006