Number of up-down permutations p of [n] such that for all i<n-1 the number of elements p(j) between p(i) and p(i+1) for j>i+1 differs from the number of elements p(k) between p(i+1) and p(i+2) for k>i+2.
A367495
Number of up-down permutations p of [n] such that for all i<n-1 the number of elements p(j) between p(i) and p(i+1) for j>i+1 differs from the number of elements p(k) between p(i+1) and p(i+2) for k>i+2.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =11a(7) =37a(8) =147a(9) =684a(10) =3611a(11) =21345a(12) =139794a(13) =1004293a(14) =7853728a(15) =66413562a(16) =603851552a(17) =5874507617a(18) =60886603188a(19) =669797203196
External references
- oeis: A367495