A242821 Number of compositions of n with equal number of even and odd parts, both counted without multiplicity.

1, 0, 0, 2, 3, 11, 14, 33, 43, 82, 141, 260, 514, 1049, 2321, 4789, 10454, 21735, 46213, 94782, 196060, 398662, 810178, 1631089, 3278372, 6556096, 13088339, 26063238, 51824061, 102926784, 204239173, 405087125, 803109813, 1592179369, 3156298826, 6258390137

Offset

0,4

Links

Alois P. Heinz, Table of n, a(n) for n = 0..500

Example

a(3) = 2: [1,2], [2,1].
a(4) = 3: [1,1,2], [1,2,1], [2,1,1].
a(5) = 11: [1,1,1,2], [1,1,2,1], [1,2,1,1], [2,1,1,1], [1,2,2], [2,1,2], [2,2,1], [2,3], [3,2], [1,4], [4,1].
a(6) = 14: [1,1,1,1,2], [1,1,1,2,1], [1,1,2,1,1], [1,2,1,1,1], [2,1,1,1,1], [1,1,2,2], [1,2,1,2], [1,2,2,1], [2,1,1,2], [2,1,2,1], [2,2,1,1], [1,1,4], [1,4,1], [4,1,1].

Crossrefs

Column k=0 of A242626.

Cf. A098123 (counted with multiplicity).

Sequence in context: A042473 A042665 A282235 * A182709 A321766 A041029

Adjacent sequences: A242818 A242819 A242820 * A242822 A242823 A242824

Keyword

nonn

Author

Alois P. Heinz, May 23 2014

Status

approved