A137737 - cp's OEIS frontend

A137737 Number of circular permutations of the multiset {1,1,2,2,...,n,n} (up to rotations) with even distances between equal elements.

n	a(n)
1	0
2	1
3	0
4	30
5	0
6	13560
7	0
8	27785520
9	0
10	162030637440
11	0
12	2156625389318400
13	0
14	56857271240920550400
15	0
16	2686506065987036477184000
17	0
18	211180868835057744408834048000
19	0
20	26072812428113877344085395644416000
21	0

[0, 1, 0, 30, 0, 13560, 0, 27785520, 0, 162030637440, 0, 2156625389318400, 0, 56857271240920550400, 0, 2686506065987036477184000, 0, 211180868835057744408834048000, 0, 26072812428113877344085395644416000, 0]

cp's OEIS Frontend

A137737 Number of circular permutations of the multiset {1,1,2,2,...,n,n} (up to rotations) with even distances between equal elements.

Table of values

List of values