A209289 - cp's OEIS frontend

A209289 Number of functions f:{1,2,...,2n}->{1,2,...,2n} such that every preimage has an even cardinality.

n	a(n)
0	1
1	2
2	40
3	2256
4	250496
5	46063360
6	12665422848
7	4866544707584
8	2490379333697536
9	1637285952230719488
10	1344814260872574402560
11	1349528279475362368847872
12	1624638302165034485761966080
13	2310920106523435237448955723776
14	3834278385523271302103123693142016

[1, 2, 40, 2256, 250496, 46063360, 12665422848, 4866544707584, 2490379333697536, 1637285952230719488, 1344814260872574402560, 1349528279475362368847872, 1624638302165034485761966080, 2310920106523435237448955723776, 3834278385523271302103123693142016]

cp's OEIS Frontend

A209289 Number of functions f:{1,2,...,2n}->{1,2,...,2n} such that every preimage has an even cardinality.

Table of values

List of values