A317140 Number of permutations of [2n+1] with exactly n increasing runs of length two.

1, 4, 43, 906, 31493, 1629248, 117248463, 11190963430, 1367267690953, 208031951035452, 38563334673062963, 8554779137299629314, 2237467931691025532493, 681305299577272105281016, 238929711424864185326131543, 95603626135129502838914478558

Offset

0,2

Links

Alois P. Heinz, Table of n, a(n) for n = 0..242

Formula

a(n) = A317139(2n+1) = A097592(2n+1,n).

a(n) + n == 1 (mod 2).

Example

a(1) = 4: 132, 213, 231, 312.

Crossrefs

Bisection (odd part) of A317139.

Cf. A097592.

Sequence in context: A074702 A197717 A277456 * A152282 A153255 A015084

Adjacent sequences: A317137 A317138 A317139 * A317141 A317142 A317143

Keyword

nonn

Author

Alois P. Heinz, Jul 22 2018

Status

approved