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 A119158 #12 Apr 06 2023 20:07:10
%S A119158 45,55,25425,255255,22542255,244525555,2245524452445,2445254445525,
%T A119158 5255545252454245,444222245455224445,4544525455555255444225,
%U A119158 5554545454254522254255544522452525245
%N A119158 Triangular numbers composed of digits {2,4,5}.
%C A119158 a(13) > 10^40.
%H A119158 G. Resta, <a href="http://www.numbersaplenty.com/tr/tr245.html">Tridigital Triangular Numbers</a>.
%F A119158 a(n) = A000217(A119159(n)).
%Y A119158 Cf. A000217, A031152, A119159. See A119033 for a table of cross-references.
%K A119158 nonn,base,more
%O A119158 1,1
%A A119158 _Giovanni Resta_, May 10 2006
%E A119158 a(12) from _Max Alekseyev_, Aug 19 2013