A241721 Number of compositions of n into distinct parts with exactly two descents.

1, 1, 2, 3, 15, 16, 29, 41, 65, 144, 179, 269, 382, 549, 739, 1286, 1564, 2254, 2978, 4124, 5304, 7264, 10157, 12941, 17027, 22194, 28663, 36884, 47306, 59837, 79467, 98114, 125117, 156392, 198113, 244710, 307908, 378429, 471337, 588642, 721300, 884498

Offset

6,3

Links

Alois P. Heinz, Table of n, a(n) for n = 6..1000

Example

a(9) = 3: [6,2,1], [5,3,1], [4,3,2].
a(10) = 15: [5,4,1], [7,2,1], [6,3,1], [5,3,2], [4,1,3,2], [2,1,4,3], [4,3,1,2], [4,2,3,1], [2,4,3,1], [1,4,3,2], [3,1,4,2], [3,2,4,1], [3,4,2,1], [4,2,1,3], [3,2,1,4].

Crossrefs

Column k=2 of A241719.

Sequence in context: A251618 A309765 A238691 * A066491 A282383 A299486

Adjacent sequences: A241718 A241719 A241720 * A241722 A241723 A241724

Keyword

nonn

Author

Alois P. Heinz, Apr 27 2014

Status

approved