The number of down-up permutations of [n] where adjacent elements differ by at least 5.
A249392
The number of down-up permutations of [n] where adjacent elements differ by at least 5.
Terms
- a(0) =1a(1) =1a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =0a(10) =1a(11) =32a(12) =1088a(13) =17280a(14) =293832a(15) =4004352a(16) =57687080a(17) =773838336a(18) =10900027949a(19) =151388845568
External references
- oeis: A249392