%I #10 Mar 19 2023 02:35:54
%S 1,21,2211,222111,1422141,4244241,22221111,44241121,124212441,
%T 2222211111,222222111111,22222221111111,1111114242224421,
%U 2222222211111111,21414424114444221,222222222111111111,1144211112222224221,22222222221111111111,44241214122411121441
%N Triangular numbers composed of digits {1,2,4}.
%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr124.html">Tridigital Triangular Numbers</a>
%F a(n) = A000217(A119100(n)). - _Michel Marcus_, Mar 19 2023
%Y Cf. A000217, A053881, A119100. See A119033 for a table of cross-references.
%K nonn,base
%O 1,2
%A _Giovanni Resta_, May 10 2006
%E a(17)-a(19) from _Tyler Busby_, Mar 18 2023