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

A177578

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

Terms

    a(0) =1a(1) =6a(2) =90a(3) =2510a(4) =111924a(5) =7292080a(6) =653417953a(7) =77078901216

External references