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 A119147 #8 Jul 13 2021 07:26:38
%S A119147 1,12,18,58,132,153,1332,1541,6018,11981,13332,40278,124753,133332,
%T A119147 603121,1332507,1333332,13332507,13333332,19072906,133332507,
%U A119147 133333332,485569333,486040907,612880278,1247972658,1333332507
%N A119147 Numbers k such that the k-th triangular number contains only digits {1,7,8}.
%H A119147 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr178.html">Tridigital Triangular Numbers</a>
%Y A119147 Cf. A000217, A119146. See A119034 for a table of cross-references.
%K A119147 nonn,base
%O A119147 1,2
%A A119147 _Giovanni Resta_, May 10 2006