A117513 - cp's OEIS frontend

A117513 Number of ways of arranging 2*n tokens in a row, with 2 copies of each token from 1 through n, such that between every pair of tokens labeled i (i = 1..n-1) there is exactly one taken labeled i+1.

n	a(n)
1	1
2	2
3	12
4	136
5	2480
6	66336
7	2446528
8	118984832
9	7378078464
10	568142287360
11	53189920492544
12	5949749335001088
13	783686338494312448
14	120058889459865165824
15	21166245289132322242560
16	4254864627502524070395904
17	967406173145278971994898432
18	247007221085479721384365129728

[1, 2, 12, 136, 2480, 66336, 2446528, 118984832, 7378078464, 568142287360, 53189920492544, 5949749335001088, 783686338494312448, 120058889459865165824, 21166245289132322242560, 4254864627502524070395904, 967406173145278971994898432, 247007221085479721384365129728]

cp's OEIS Frontend

A117513 Number of ways of arranging 2*n tokens in a row, with 2 copies of each token from 1 through n, such that between every pair of tokens labeled i (i = 1..n-1) there is exactly one taken labeled i+1.

Table of values

List of values