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 A119137 #8 Jul 13 2021 07:28:32
%S A119137 1,5,10,101,130,1078,1330,1541,4730,10114,12773,13330,41269,133330,
%T A119137 1333330,13333330,133333330,1333333330,3430798394,5506103010,
%U A119137 13333333330,108245601470,133333333330,1305029950270,1333333333330
%N A119137 Numbers k such that the k-th triangular number contains only digits {1,5,8}.
%H A119137 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr158.html">Tridigital Triangular Numbers</a>
%Y A119137 Cf. A000217, A119136. See A119034 for a table of cross-references.
%K A119137 nonn,base
%O A119137 1,2
%A A119137 _Giovanni Resta_, May 10 2006