A200047 Number of compositions of n having smallest part equal to 2.

0, 1, 0, 1, 2, 3, 5, 9, 15, 25, 42, 70, 116, 192, 317, 522, 858, 1408, 2307, 3775, 6170, 10074, 16433, 26784, 43623, 71002, 115497, 187777, 305147, 495669, 804839, 1306404, 2119884, 3438952, 5577396, 9043549, 14660810, 23762784, 38509220, 62397495, 101090631

Offset

1,5

Links

Alois P. Heinz, Table of n, a(n) for n = 1..1000

Formula

G.f.: (x-1)^2*x^2/(1-2*x+x^4+x^5).

Example

a(7) = 5: [2,2,3], [2,3,2], [2,5], [3,2,2], [5,2].

Maple

a:= n-> (<<0|1|0|0|0>, <0|0|1|0|0>, <0|0|0|1|0>, <0|0|0|0|1>, <-1|-1|0|0|2>>^n. <<0, 0, 1, 0, 1>>)[1, 1]: seq (a(n), n=1..50);

Crossrefs

Column k=2 of A105147.

Sequence in context: A097083 A268709 A326024 * A147877 A003476 A017989

Adjacent sequences: A200044 A200045 A200046 * A200048 A200049 A200050

Keyword

nonn

Author

Alois P. Heinz, Nov 13 2011

Status

approved