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Triangular numbers composed of digits {1,2,4}.
2

%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