A272261 - cp's OEIS frontend

A272261 Number of one-to-one functions f from [n] to [2n] where f(x) may not be equal to x or to 2n+1-x.

n	a(n)
0	1
1	0
2	4
3	40
4	576
5	10528
6	233920
7	6124032
8	184656640
9	6302821888
10	240245858304
11	10115537336320
12	466275700903936
13	23354247194542080
14	1262994451308888064
15	73347095164693676032
16	4552571878016243466240
17	300763132329730843475968
18	21071629550593224017182720

[1, 0, 4, 40, 576, 10528, 233920, 6124032, 184656640, 6302821888, 240245858304, 10115537336320, 466275700903936, 23354247194542080, 1262994451308888064, 73347095164693676032, 4552571878016243466240, 300763132329730843475968, 21071629550593224017182720]

cp's OEIS Frontend

A272261 Number of one-to-one functions f from [n] to [2n] where f(x) may not be equal to x or to 2n+1-x.

Table of values

List of values