Triangular array read by rows. T(n,k) is the number of ways to choose a size k subset S of [n] and form a labeled acyclic digraph on S. Then form another labeled acyclic digraph on [n]-S. For each pair u in S and v in [n]-S add the directed edge u->v or not, n>=0, 0<=k<=n.

A380336

Triangular array read by rows. T(n,k) is the number of ways to choose a size k subset S of [n] and form a labeled acyclic digraph on S. Then form another labeled acyclic digraph on [n]-S. For each pair u in S and v in [n]-S add the directed edge u->v or not, n>=0, 0<=k<=n.