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 A119102 #8 Jul 13 2021 01:24:38
%S A119102 1,5,6,10,49,66,101,174,205,210,550,666,714,4806,5010,6498,6666,10114,
%T A119102 14914,22410,66666,71449,471701,495005,666666,1500101,2246130,3241950,
%U A119102 6666666,15591825,17408114,66666666,666666666,1024813373,1581866714
%N A119102 Numbers k such that the k-th triangular number contains only digits {1,2,5}.
%H A119102 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr125.html">Tridigital Triangular Numbers</a>
%Y A119102 Cf. A000217, A119101. See A119034 for a table of cross-references.
%K A119102 nonn,base
%O A119102 1,2
%A A119102 _Giovanni Resta_, May 10 2006