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

Author

Alois P. Heinz, May 23 2014

Keywords

• nonn

Examples

			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].
		

Links

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

Crossrefs

Column k=0 of A242626.

Cf. A098123 (counted with multiplicity).