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

A177589

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

Terms

    a(0) =1a(1) =6a(2) =90a(3) =2520a(4) =113256a(5) =7457040a(6) =676387059a(7) =80853167472

External references