A209036 - cp's OEIS frontend

A209036 Number of permutations of the multiset {1,1,2,2,....,n,n} with exactly two consecutive equal terms.

n	a(n)
1	1
2	2
3	36
4	984
5	43800
6	2868480
7	259554960
8	31012490880
9	4728875800320
10	896042510496000
11	206523228759724800
12	56893926736333209600
13	18461230471787348044800
14	6968851610446509386803200

[1, 2, 36, 984, 43800, 2868480, 259554960, 31012490880, 4728875800320, 896042510496000, 206523228759724800, 56893926736333209600, 18461230471787348044800, 6968851610446509386803200]

cp's OEIS Frontend

A209036 Number of permutations of the multiset {1,1,2,2,....,n,n} with exactly two consecutive equal terms.

Table of values

List of values