Number of 4 up, 4 down, 4 up, ... permutations of length 4n+1.

A005983

Number of 4 up, 4 down, 4 up, ... permutations of length 4n+1.

Terms

    a(0) =1a(1) =1a(2) =70a(3) =26599a(4) =33757360a(5) =107709888805

External references