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 A119078 #8 Jul 13 2021 01:25:25
%S A119078 44,2831780,1407437419,140715344155
%N A119078 Numbers k such that the k-th triangular number contains only digits {0,4,9}.
%C A119078 Next term exceeds 1.4*10^16.
%H A119078 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr049.html">Tridigital Triangular Numbers</a>
%Y A119078 Cf. A000217, A119077. See A119034 for a table of cross-references.
%K A119078 nonn,base,more
%O A119078 1,1
%A A119078 _Giovanni Resta_, May 10 2006