A209319 - cp's OEIS frontend

A209319 Number of functions f:{1,2,...,n}->{1,2,...,n} whose cycle lengths are <= 2.

n	a(n)
0	1
1	1
2	4
3	25
4	218
5	2451
6	33832
7	554527
8	10535100
9	227790505
10	5525843696
11	148673435769
12	4394818486456
13	141611317636075
14	4940870266568160
15	185595910032346111
16	7468517348971708688
17	320562141349559055633
18	14619577651630443611200
19	706025600924216704982425

[1, 1, 4, 25, 218, 2451, 33832, 554527, 10535100, 227790505, 5525843696, 148673435769, 4394818486456, 141611317636075, 4940870266568160, 185595910032346111, 7468517348971708688, 320562141349559055633, 14619577651630443611200, 706025600924216704982425]

cp's OEIS Frontend

A209319 Number of functions f:{1,2,...,n}->{1,2,...,n} whose cycle lengths are <= 2.

Table of values

List of values