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 A119141 #8 Jul 13 2021 07:28:39
%S A119141 1,3,11,18,36,48,58,188,351,366,576,1111,3941,11106,12423,17981,18263,
%T A119141 34976,365423,392711,585963,1111411,1494106,568817576,1494099506,
%U A119141 3651623506,12382820048,351330663666,586117934576,37888432565023
%N A119141 Numbers k such that the k-th triangular number contains only digits {1,6,7}.
%H A119141 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr167.html">Tridigital Triangular Numbers</a>
%Y A119141 Cf. A000217, A119140. See A119034 for a table of cross-references.
%K A119141 nonn,base
%O A119141 1,2
%A A119141 _Giovanni Resta_, May 10 2006