A242840 Number of compositions of n with difference -1 between the number of odd parts and the number of even parts, both counted without multiplicity.

1, 0, 2, 0, 2, 6, 15, 44, 74, 202, 351, 766, 1301, 2626, 4677, 8993, 16466, 31671, 60266, 116751, 229180, 452667, 905627, 1815394, 3673666, 7429123, 15109955, 30696510, 62512866, 127140993, 258745131, 525845884, 1068309682, 2167462318, 4393853912, 8896007640

Offset: 2

Author

Alois P. Heinz, May 23 2014

Keywords

• nonn

Examples

			a(2) = 1: [2].
a(4) = 2: [2,2], [4].
a(6) = 2: [2,2,2], [6].
a(7) = 6: [1,2,4], [1,4,2], [2,1,4], [2,4,1], [4,1,2], [4,2,1].
a(8) = 15: [2,2,2,2], [1,1,2,4], [1,1,4,2], [1,2,1,4], [1,2,4,1], [1,4,1,2], [1,4,2,1], [2,1,1,4], [2,1,4,1], [2,4,1,1], [4,1,1,2], [4,1,2,1], [4,2,1,1], [4,4], [8].
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 2..500

Crossrefs

Column k=-1 of A242626.