Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, up, down.
A177577
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, up, down.
Terms
- a(0) =1a(1) =6a(2) =90a(3) =2502a(4) =110892a(5) =7173916a(6) =637847566a(7) =74626447992
External references
- oeis: A177577