A119186 - OEIS

%I #11 Mar 24 2023 17:14:44

%S 3,6,36,55,66,666,3655,5356,5565,6555,333336,3635556,5656566,35536665,

%T 56365653,56663335,63365653,655636366,53533355655,55663663653,

%U 533533653555,555533363556,6653355565366,555665666566566,35356355566555653,653366333366663536656

%N Triangular numbers composed of digits {3,5,6}.

%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr356.html">Tridigital Triangular Numbers</a>

%F a(n) = A000217(A119187(n)). - _Tyler Busby_, Mar 24 2023

%t Table[Select[FromDigits/@Tuples[{3,5,6},n],OddQ[Sqrt[8#+1]]&],{n,15}]//Flatten (* _Harvey P. Dale_, Aug 03 2021 *)

%Y Cf. A000217, A053945, A119187. See A119033 for a table of cross-references.

%K nonn,base

%O 1,1

%A _Giovanni Resta_, May 10 2006

%E a(25)-a(26) from _Tyler Busby_, Mar 24 2023