Triangle read by rows: T(n,k) is the number of permutations pi of [n] with k+1 valleys such that s(pi) avoids the patterns 132, 231, 312, and 321, where s denotes West's stack-sorting map (0 <= k <= floor((n-1)/2)).

A319252

Triangle read by rows: T(n,k) is the number of permutations pi of [n] with k+1 valleys such that s(pi) avoids the patterns 132, 231, 312, and 321, where s denotes West's stack-sorting map (0 <= k <= floor((n-1)/2)).