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 A119207 #7 Jul 13 2021 21:30:09
%S A119207 9,10,9854,411933209,9443035090314,29851116744790,30195643554810,
%T A119207 3423114221246070
%N A119207 Numbers k such that the k-th triangular number contains only digits {4,5,8}.
%C A119207 Next term exceeds 1.4*10^16.
%H A119207 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr458.html">Tridigital Triangular Numbers</a>
%Y A119207 Cf. A000217, A119206. See A119034 for a table of cross-references.
%K A119207 nonn,base,more
%O A119207 1,1
%A A119207 _Giovanni Resta_, May 10 2006