Number of permutations of 1..n avoiding adjacent step pattern up, down, down, down.
A177518
Number of permutations of 1..n avoiding adjacent step pattern up, down, down, down.
Terms
- a(0) =1a(1) =2a(2) =6a(3) =24a(4) =116a(5) =672a(6) =4536a(7) =34944a(8) =302896a(9) =2916992a(10) =30899616a(11) =357080064a(12) =4470310976a(13) =60269056512a(14) =870591770496
External references
- oeis: A177518