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

A137730

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

Terms

    a(0) =1a(1) =1a(2) =7a(3) =72a(4) =1452a(5) =43200a(6) =1814760a(7) =101606400a(8) =7315680960a(9) =658409472000

External references