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A241721
Number of compositions of n into distinct parts with exactly two descents.
2
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
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
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Apr 27 2014
STATUS
approved