Number of permutations of 2 copies of 1..n with all adjacent differences <= 4 in absolute value.

A177285

Number of permutations of 2 copies of 1..n with all adjacent differences <= 4 in absolute value.

Terms

    a(0) =1a(1) =1a(2) =6a(3) =90a(4) =2520a(5) =113400a(6) =3356640a(7) =75336660a(8) =1500131820a(9) =29660400822a(10) =620330067782

External references