Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, down.

A177565

Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, down.

Terms

    a(0) =1a(1) =6a(2) =90a(3) =2520a(4) =112920a(5) =7398873a(6) =667165914a(7) =79232435816

External references