3 up, 3 down, 3 up, ... permutations of length 3n+1.

A005982

3 up, 3 down, 3 up, ... permutations of length 3n+1.

Terms

    a(0) =1a(1) =20a(2) =1301a(3) =202840a(4) =61889101a(5) =32676403052

External references