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 A119089 #16 May 02 2023 23:50:21
%S A119089 6,66,666,66066,600060,808080868686,6800080088880,600060808600606,
%T A119089 6866666600888008866,8868600066880068688680,66888008886880660860006,
%U A119089 8068888000086860008866800600800680,888806860800600880800086860880800680,8006680886068066868608660888886880660
%N A119089 Triangular numbers composed of digits {0,6,8}.
%C A119089 a(15) > 10^40. - _Tyler Busby_, Mar 15 2023
%H A119089 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr068.html">Tridigital Triangular Numbers</a>
%F A119089 a(n) = A000217(A119090(n)). - _Michel Marcus_, Mar 16 2023
%Y A119089 Cf. A000217, A119090. See A119033 for a table of cross-references.
%K A119089 nonn,base
%O A119089 1,1
%A A119089 _Giovanni Resta_, May 10 2006
%E A119089 a(12)-a(14) from _Tyler Busby_, Mar 15 2023