A001887 - cp's OEIS frontend

A001887 Number of permutations p of {1,2,...,n} such that p(i) - i < 0 or p(i) - i > 2 for all i.

n	a(n)
0	1
1	0
2	0
3	0
4	1
5	5
6	33
7	236
8	1918
9	17440
10	175649
11	1942171
12	23396353
13	305055960
14	4280721564
15	64330087888
16	1030831875953
17	17545848553729
18	316150872317105
19	6012076099604308
20	120330082937778554

[1, 0, 0, 0, 1, 5, 33, 236, 1918, 17440, 175649, 1942171, 23396353, 305055960, 4280721564, 64330087888, 1030831875953, 17545848553729, 316150872317105, 6012076099604308, 120330082937778554]

cp's OEIS Frontend

A001887 Number of permutations p of {1,2,...,n} such that p(i) - i < 0 or p(i) - i > 2 for all i.

Table of values

List of values