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

A177555

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

Terms

    a(0) =1a(1) =1a(2) =6a(3) =67a(4) =1345a(5) =42540a(6) =1954681a(7) =123179785a(8) =10202958366

External references