Number of permutations of 3 copies of 1..n introduced in order 1..n with no element equal to another within a distance of 2.

A190827

Number of permutations of 3 copies of 1..n introduced in order 1..n with no element equal to another within a distance of 2.

Terms

    a(0) =0a(1) =0a(2) =1a(3) =109a(4) =12721a(5) =2001240a(6) =418539642a(7) =113320421342

External references