Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, up.
A177562
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, up.
Terms
- a(0) =1a(1) =6a(2) =84a(3) =2123a(4) =84034a(5) =4804627a(6) =375435365a(7) =38463186965
External references
- oeis: A177562