A384561 - cp's OEIS frontend

A384561 One fourth of the number of permutations of [n] with |p(i+1) - p(i)| >= 2, for i = 1..(n-1) and n appears at position i = 1 or i = n.

n	a(n)
5	1
6	6
7	39
8	284
9	2337
10	21474
11	218179
12	2430216
13	29459301
14	386182478
15	5444570631
16	82157021556
17	1321282006249
18	22562446559034
19	407722012334667
20	7773697259015264
21	155956589714240109
22	3284208113313605286
23	72434065593967762831
24	1669777527837108720588
25	40157785493048522566641

[1, 6, 39, 284, 2337, 21474, 218179, 2430216, 29459301, 386182478, 5444570631, 82157021556, 1321282006249, 22562446559034, 407722012334667, 7773697259015264, 155956589714240109, 3284208113313605286, 72434065593967762831, 1669777527837108720588, 40157785493048522566641]

cp's OEIS Frontend

A384561 One fourth of the number of permutations of [n] with |p(i+1) - p(i)| >= 2, for i = 1..(n-1) and n appears at position i = 1 or i = n.

Table of values

List of values