Voozh

A119202

Triangular numbers composed of digits {4,5,6}.

6, 45, 55, 66, 465, 666, 4465, 4656, 5565, 6555, 46665, 544446, 4465566, 5456556, 5656566, 64564566, 4565545455565, 4664644554466, 56466665456545, 555445466565465, 555445666545666, 555665666566566, 4446456564566646, 6666664664655666, 46566644555566656

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..25.

Giovanni Resta, Tridigital Triangular Numbers.

FORMULA

a(n) = A000217(A119203(n)). - Tyler Busby, Mar 25 2023

MATHEMATICA

Table[Select[FromDigits/@Tuples[{4, 5, 6}, n], OddQ[Sqrt[8#+1]]&], {n, 17}]//Flatten (* Harvey P. Dale, Aug 28 2023 *)

CROSSREFS

Cf. A000217, A030176, A119203. See A119033 for a table of cross-references.