A356832 - cp's OEIS frontend

A356832 Number of permutations p of [n] such that at most one element of {p(1),...,p(i-1)} is between p(i) and p(i+1) for all i < n and n = 0 or p(n) < 3.

n	a(n)
0	1
1	1
2	2
3	4
4	10
5	26
6	72
7	206
8	608
9	1834
10	5636
11	17578
12	55516
13	177192
14	570700
15	1852572
16	6055080
17	19910730
18	65823752
19	218654100
20	729459552
21	2443051214
22	8210993364
23	27685671844
24	93625082140
25	317470233150
26	1079183930828
27	3676951654520
28	12554734605496
29	42952566314236

[1, 1, 2, 4, 10, 26, 72, 206, 608, 1834, 5636, 17578, 55516, 177192, 570700, 1852572, 6055080, 19910730, 65823752, 218654100, 729459552, 2443051214, 8210993364, 27685671844, 93625082140, 317470233150, 1079183930828, 3676951654520, 12554734605496, 42952566314236]

cp's OEIS Frontend

A356832 Number of permutations p of [n] such that at most one element of {p(1),...,p(i-1)} is between p(i) and p(i+1) for all i < n and n = 0 or p(n) < 3.

Table of values

List of values