A134362 - cp's OEIS frontend

A134362 a(n) is the number of functions f:X->X, where |X| = n, such that for every x in X, f(f(x)) != x (i.e., the square of the function has no fixed points; note this implies that the function has no fixed points).

n	a(n)
0	1
1	0
2	0
3	2
4	30
5	444
6	7360
7	138690
8	2954364
9	70469000
10	1864204416
11	54224221050
12	1721080885480
13	59217131089908
14	2195990208122880
15	87329597612123594
16	3707783109757616400
17	167411012044894728720
18	8010372386879991018496
19	404912918159552083622130

[1, 0, 0, 2, 30, 444, 7360, 138690, 2954364, 70469000, 1864204416, 54224221050, 1721080885480, 59217131089908, 2195990208122880, 87329597612123594, 3707783109757616400, 167411012044894728720, 8010372386879991018496, 404912918159552083622130]

cp's OEIS Frontend

A134362 a(n) is the number of functions f:X->X, where |X| = n, such that for every x in X, f(f(x)) != x (i.e., the square of the function has no fixed points; note this implies that the function has no fixed points).

Table of values

List of values