One fourth of the number of permutations of [n] with |p(i+1) - p(i)| >= 2, for i = 1..(n-1) and n appears at position i = 1 or i = n.
A384561
One fourth of the number of permutations of [n] with |p(i+1) - p(i)| >= 2, for i = 1..(n-1) and n appears at position i = 1 or i = n.
Terms
- a(0) =1a(1) =6a(2) =39a(3) =284a(4) =2337a(5) =21474a(6) =218179a(7) =2430216a(8) =29459301a(9) =386182478a(10) =5444570631a(11) =82157021556
External references
- oeis: A384561