Number of permutations of the multiset {1,1,2,2,....,n,n} with exactly two consecutive equal terms.
A209036
Number of permutations of the multiset {1,1,2,2,....,n,n} with exactly two consecutive equal terms.
Terms
- a(0) =1a(1) =2a(2) =36a(3) =984a(4) =43800a(5) =2868480a(6) =259554960a(7) =31012490880
External references
- oeis: A209036