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 A119070 #8 Jul 13 2021 01:25:13
%S A119070 2,24,42,44,77,260,282,824,1364,8835,44517,88419,89375,256917,282842,
%T A119070 426600,2603844,14141435,424287482,894359435,24629287602,81351102024,
%U A119070 137064943244,1371082295364,2489711201364,8870066515082
%N A119070 Numbers k such that the k-th triangular number contains only digits {0,3,9}.
%H A119070 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr039.html">Tridigital Triangular Numbers</a>
%Y A119070 Cf. A000217, A119069. See A119034 for a table of cross-references.
%K A119070 nonn,base
%O A119070 1,1
%A A119070 _Giovanni Resta_, May 10 2006