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

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers

Crossrefs

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

Programs

Mathematica

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

Formula

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

Extensions

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

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