n-alternating permutations of length 3n.

A211213

n-alternating permutations of length 3n.

Terms

    a(0) =1a(1) =61a(2) =1513a(3) =33661a(4) =750751a(5) =17116009a(6) =398840401a(7) =9464040829a(8) =227864057851

External references