Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, up, up.
A177558
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, up, up.
Terms
- a(0) =1a(1) =1a(2) =6a(3) =90a(4) =2401a(5) =101761a(6) =6291216a(7) =534649500a(8) =59805912601
External references
- oeis: A177558