A388149 Number of partial permutations of [2n] that have exactly n cycles.

1, 3, 41, 965, 32179, 1387617, 73376435, 4595401239, 332576767523, 27309220303937, 2508532874244891, 254868083994804007, 28378575132862651917, 3436475259153967695095, 449643047382070812141885, 63218449394701421070509745, 9505029949439482326271983795

Offset

0,2

Links

Alois P. Heinz, Table of n, a(n) for n = 0..326

Formula

a(n) = (2n)! * [x^(2n) y^n] exp(x/(1-x))/(1-x)^y.

a(n) = A216294(2n,n).

Crossrefs

Cf. A216294.

Sequence in context: A138961 A075022 A367981 * A300281 A012175 A007313

Adjacent sequences: A388146 A388147 A388148 * A388150 A388151 A388152

Keyword

nonn

Author

Alois P. Heinz, Sep 15 2025

Status

approved