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

A322179

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

Terms

    a(0) =1a(1) =0a(2) =0a(3) =2a(4) =40a(5) =1070a(6) =38936a(7) =1896220a(8) =119912476a(9) =9587033840

External references