A119103 Triangular numbers composed of digits {1,2,6}.

1, 6, 21, 66, 666, 2211, 6216, 212226, 222111, 1222266, 1261666, 16626261, 22121226, 22221111, 121111266, 126222216, 661261161, 2162616261, 2221211226, 2222211111, 21166222626, 66126661611, 166122226621, 216262612611, 222212111226, 222222111111, 22162261612611

Offset

1,2

Links

Table of n, a(n) for n=1..27.

Giovanni Resta, Tridigital Triangular Numbers

Formula

a(n) = A000217(A119104(n)). - Michel Marcus, Mar 16 2023

Mathematica

Flatten[Table[Select[FromDigits/@Tuples[{1, 2, 6}, n], OddQ[Sqrt[8#+1]]&], {n, 12}]] (* Harvey P. Dale, Mar 07 2015 *)

Crossrefs

Cf. A000217, A053883, A119104. See A119033 for a table of cross-references.

Sequence in context: A117962 A105457 A134931 * A180795 A306089 A107653

Adjacent sequences: A119100 A119101 A119102 * A119104 A119105 A119106

Keyword

nonn,base

Author

Giovanni Resta, May 10 2006

Extensions

a(24)-a(27) from Tyler Busby, Mar 14 2023

Status

approved