The number of permutations of {1,2,...,n,1,2,...,n} with the property that there are k or fewer numbers between the two k's in the set for k=1,...,n.

A322180

The number of permutations of {1,2,...,n,1,2,...,n} with the property that there are k or fewer numbers between the two k's in the set for k=1,...,n.

Terms

    a(0) =1a(1) =1a(2) =5a(3) =36a(4) =466a(5) =8942a(6) =240366a(7) =8576860a(8) =392952468a(9) =22470271108

External references