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 A119088 #8 Jul 13 2021 01:24:14
%S A119088 3,11,36,115,363,1095,11576,36624,363504,391576,391588,36333648,
%T A119088 123288823,3660785999,11014541352775,39410677756315,124633627940188
%N A119088 Numbers k such that the k-th triangular number contains only digits {0,6,7}.
%C A119088 Next term exceeds 1.4*10^16.
%H A119088 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr067.html">Tridigital Triangular Numbers</a>
%Y A119088 Cf. A000217, A119087. See A119034 for a table of cross-references.
%K A119088 nonn,base,more
%O A119088 1,1
%A A119088 _Giovanni Resta_, May 10 2006