A091605 Column 2 of triangle A091602.

1, 0, 2, 2, 3, 4, 7, 8, 12, 15, 21, 26, 35, 43, 57, 70, 89, 109, 138, 167, 208, 251, 309, 371, 452, 539, 652, 775, 929, 1099, 1311, 1543, 1829, 2146, 2529, 2957, 3469, 4040, 4721, 5481, 6377, 7381, 8559, 9875, 11412, 13133, 15128, 17364, 19945, 22833

Offset

2,3

Links

Alois P. Heinz, Table of n, a(n) for n = 2..1000

Formula

a(n) = A000726(n) - A000009(n).

Example

a(7) counts these partitions:  511, 331, 322, 3211. - Clark Kimberling, Mar 10 2014

Mathematica

d[n_] := Select[IntegerPartitions[n], Max[Length /@ Split@#] == 2 &];
t = Table[d[n], {n, 12}]  (* shows partitions *)
u = Table[Length[d[n]], {n, 2, 30}] (* counts partitions *)
(* Clark Kimberling, Mar 10 2014 *)

Crossrefs

Sequence in context: A058670 A215367 A276526 * A145468 A125554 A345867

Adjacent sequences: A091602 A091603 A091604 * A091606 A091607 A091608

Keyword

nonn

Author

Christian G. Bower, Jan 23 2004

Status

approved