A356853 - cp's OEIS frontend

A356853 Number of permutations p of [2n+1] such that at most one element of {p(1),...,p(i-1)} is between p(i) and p(i+1) for all i <= 2n and p(2n+1) = n+1.

n	a(n)
0	1
1	2
2	20
3	216
4	2720
5	36228
6	503216
7	7171404
8	104142520
9	1533200656
10	22811374568
11	342216338652
12	5168324302672
13	78483423004680
14	1197266739443160
15	18335055482658748
16	281714880491273736
17	4340894020114398672
18	67055152953864109240
19	1038097819961270208088

[1, 2, 20, 216, 2720, 36228, 503216, 7171404, 104142520, 1533200656, 22811374568, 342216338652, 5168324302672, 78483423004680, 1197266739443160, 18335055482658748, 281714880491273736, 4340894020114398672, 67055152953864109240, 1038097819961270208088]

cp's OEIS Frontend

A356853 Number of permutations p of [2n+1] such that at most one element of {p(1),...,p(i-1)} is between p(i) and p(i+1) for all i <= 2n and p(2n+1) = n+1.

Table of values

List of values