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 A119171 #12 Mar 31 2023 02:41:02
%S A119171 10,34,109,714,765,774,227825,14092049,334531090,33345441365,
%T A119171 1360847497350,102951958915365,3462935043926049509,4455459562273973825
%N A119171 Numbers k such that the k-th triangular number contains only digits {2,5,9}.
%H A119171 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr259.html">Tridigital Triangular Numbers</a>.
%Y A119171 Cf. A000217, A119170. See A119034 for a table of cross-references.
%K A119171 nonn,base,more
%O A119171 1,1
%A A119171 _Giovanni Resta_, May 10 2006
%E A119171 a(13)-a(14) from _Tyler Busby_, Mar 31 2023