A137749 - cp's OEIS frontend

A137749 Number of circular permutations of the multiset {1,1,2,2,...,2n,2n} (up to rotations) with even distances between equal elements.

n	a(n)
1	1
2	30
3	13560
4	27785520
5	162030637440
6	2156625389318400
7	56857271240920550400
8	2686506065987036477184000
9	211180868835057744408834048000
10	26072812428113877344085395644416000
11	4829206317935252350431489703482654720000

[1, 30, 13560, 27785520, 162030637440, 2156625389318400, 56857271240920550400, 2686506065987036477184000, 211180868835057744408834048000, 26072812428113877344085395644416000, 4829206317935252350431489703482654720000]

cp's OEIS Frontend

A137749 Number of circular permutations of the multiset {1,1,2,2,...,2n,2n} (up to rotations) with even distances between equal elements.

Table of values

List of values