On the Number of Delaunay Triangles occurring in all Contiguous Subsequences

Given an ordered sequence of points P = {p1, p2, . . . pn}, we are interested in the number of different Delaunay triangles occurring when considering the Delaunay triangulations of all contiguous subsequences within P . While clearly point sets and orderings with Θ(n2) Delaunay triangles exist, we prove that for an arbitrary point set in random order, the expected number of Delaunay triangles is Θ(n logn).