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

2,3

Links

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

Example

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].

Crossrefs

Column k=-1 of A242626.

Sequence in context: A175802 A161803 A057980 * A081081 A111111 A185343

Adjacent sequences: A242837 A242838 A242839 * A242841 A242842 A242843

Keyword

nonn

Author

Alois P. Heinz, May 23 2014

Status

approved