A119125 Triangular numbers composed of digits {1,4,6}.

1, 6, 66, 666, 6441, 41616, 146611, 464166, 1464616, 4114146, 14116641, 664611111, 1164441411, 16646464416, 41641661166, 66114661161, 144161141446, 161646441166, 1464464661166, 4464411144441, 44416146616416, 61116114144646, 466141616644641, 1116644466666141, 1161666441164166

Offset

1,2

Links

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

Giovanni Resta, Tridigital Triangular Numbers

Formula

a(n) = A000217(A119126(n)). - Michel Marcus, Mar 22 2023

Mathematica

Table[Select[FromDigits/@Tuples[{1, 4, 6}, n], OddQ[Sqrt[8#+1]]&], {n, 16}]//Flatten (* Harvey P. Dale, Jun 20 2023 *)

Crossrefs

Cf. A000217, A027676, A119126. See A119033 for a table of cross-references.

Sequence in context: A119100 A119176 A155630 * A137120 A002280 A073548

Adjacent sequences: A119122 A119123 A119124 * A119126 A119127 A119128

Keyword

nonn,base

Author

Giovanni Resta, May 10 2006

Extensions

a(22)-a(24) from Tyler Busby, Mar 22 2023

a(25) from Harvey P. Dale, Jun 20 2023

Status

approved