Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, up, down, down.
A177563
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, up, down, down.
Terms
- a(0) =1a(1) =6a(2) =88a(3) =2328a(4) =96886a(5) =5841912a(6) =482051408a(7) =52197308928
External references
- oeis: A177563