Number of circular permutations of the multiset {1,1,2,2,...,n,n} (up to rotations) with even distances between equal elements.
A137737
Number of circular permutations of the multiset {1,1,2,2,...,n,n} (up to rotations) with even distances between equal elements.
Terms
- a(0) =0a(1) =1a(2) =0a(3) =30a(4) =0a(5) =13560a(6) =0a(7) =27785520a(8) =0a(9) =162030637440a(10) =0a(12) =0a(14) =0a(16) =0a(18) =0a(20) =0
External references
- oeis: A137737