Array read by antidiagonals: T(n,k)=number of permutations p() of 1..n+k with centered difference p(i+1)-p(i-1) < 0 exactly k-1 times.

A180887

Array read by antidiagonals: T(n,k)=number of permutations p() of 1..n+k with centered difference p(i+1)-p(i-1) < 0 exactly k-1 times.

Terms

    a(0) =2a(1) =3a(2) =3a(3) =6a(4) =12a(5) =6a(6) =10a(7) =50a(8) =50a(9) =10a(10) =20a(11) =160a(12) =360a(13) =160a(14) =20a(15) =35a(16) =525a(17) =1960a(18) =1960a(19) =525a(20) =35a(21) =70a(22) =1540a(23) =10010a(24) =17080a(25) =10010a(26) =1540a(27) =70a(28) =126a(29) =4662

External references