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 A119075 #22 Mar 28 2023 19:00:24
%S A119075 80080840,4448084040,804844884480,4448404804004804800840804848000,
%T A119075 44804084840840840848040408400000
%N A119075 Triangular numbers composed of digits {0,4,8}.
%C A119075 a(6) > 10^37. - _Max Alekseyev_, May 17 2009
%C A119075 a(6) > 10^40. - _Tyler Busby_, Mar 28 2023
%H A119075 Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr048.html">Tridigital Triangular Numbers</a>.
%F A119075 a(n) = A000217(A119076(n)). - _Michel Marcus_, Mar 27 2023
%t A119075 Rest[Select[FromDigits/@Tuples[{0, 4, 8}, 12], IntegerQ[(Sqrt[8 # + 1] - 1)/2] &]] (* _Vincenzo Librandi_, Dec 18 2015 *)
%o A119075 (Magma) [t: n in [1..2*10^7] | Set(Intseq(t)) subset {0, 4, 8} where t is n*(n+1) div 2]; // _Vincenzo Librandi_, Dec 18 2015
%Y A119075 Cf. A000217, A058442, A119076. See A119033 for a table of cross-references.
%K A119075 nonn,base,more
%O A119075 1,1
%A A119075 _Giovanni Resta_, May 10 2006