A119097 Triangular numbers composed of digits {1,2,3}.

1, 3, 21, 231, 2211, 3321, 21321, 32131, 222111, 232221, 11132121, 22221111, 22321221, 2222211111, 2223211221, 12221332311, 222222111111, 222232111221, 1121113113121, 1231322213121, 22222221111111, 22222321111221, 2222222211111111, 2222223211111221

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A030174, A119098. See A119033 for a table of cross-references.

Programs

Mathematica

Flatten[Table[Select[FromDigits/@Tuples[{1,2,3},n],IntegerQ[(Sqrt[ 8#+1]- 1)/2]&],{n,14}]] (* Harvey P. Dale, May 16 2014 *)

Formula

a(n) = A000217(A119098(n)). - Tyler Busby, Mar 31 2023

Extensions

a(23)-a(24) from Tyler Busby, Mar 23 2023