Number of permutations of 1..n avoiding adjacent step pattern up, down, up, down.
A177520
Number of permutations of 1..n avoiding adjacent step pattern up, down, up, down.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =104a(6) =528a(7) =3296a(8) =23168a(9) =179712a(10) =1573632a(11) =15207424a(12) =158880768a(13) =1801996288a(14) =22088716288a(15) =289379395584
External references
- oeis: A177520