The number of down-up permutations of [n] where adjacent elements differ by at least 3.
A249390
The number of down-up permutations of [n] where adjacent elements differ by at least 3.
Terms
- a(0) =1a(1) =1a(2) =0a(3) =0a(4) =0a(5) =0a(6) =1a(7) =8a(8) =68a(9) =480a(10) =3637a(11) =27968a(12) =231410a(13) =2014784a(14) =18789010a(15) =185234176a(16) =1943243785a(17) =21501237248a(18) =251589065328
External references
- oeis: A249390