Number of permutations of 1..n avoiding adjacent step pattern up, down, down, up.
A177519
Number of permutations of 1..n avoiding adjacent step pattern up, down, down, up.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =109a(6) =588a(7) =3654a(8) =26125a(9) =209863a(10) =1876502a(11) =18441367a(12) =197776850a(13) =2297242583a(14) =28739304385a(15) =385195455471
External references
- oeis: A177519