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 A119206 #12 Mar 29 2023 17:17:02
%S A119206 45,55,48555585,84844484544485445,44585455858455488585854455,
%T A119206 445544585455555888554444445,455888444844584444558845455,
%U A119206 5858855485848545848448855845485
%N A119206 Triangular numbers composed of digits {4,5,8}.
%C A119206 a(9) > 10^40. - _Tyler Busby_, Mar 29 2023
%H A119206 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr458.html">Tridigital Triangular Numbers</a>.
%F A119206 a(n) = A000217(A119207(n)). - _Jon E. Schoenfield_, Mar 27 2023
%Y A119206 Cf. A000217, A053953, A119207. See A119033 for a table of cross-references.
%K A119206 nonn,base,more
%O A119206 1,1
%A A119206 _Giovanni Resta_, May 10 2006