A120928 - cp's OEIS frontend

A120928 Number of "ups" and "downs" in the permutations of [n] if either a previous counted "up" ("down") or a "void" precedes an "up" ("down") which then will be counted also.

n	a(n)
2	2
3	8
4	44
5	280
6	2040
7	16800
8	154560
9	1572480
10	17539200
11	212889600
12	2794176000
13	39437798400
14	595718323200
15	9589612032000
16	163895187456000
17	2964061900800000
18	56554301067264000
19	1135354270482432000
20	23923536413736960000
21	527939735774330880000

[2, 8, 44, 280, 2040, 16800, 154560, 1572480, 17539200, 212889600, 2794176000, 39437798400, 595718323200, 9589612032000, 163895187456000, 2964061900800000, 56554301067264000, 1135354270482432000, 23923536413736960000, 527939735774330880000]

cp's OEIS Frontend

A120928 Number of "ups" and "downs" in the permutations of [n] if either a previous counted "up" ("down") or a "void" precedes an "up" ("down") which then will be counted also.

Table of values

List of values