Computing the diversity vectors of balls of a given graph

For an ordinary finite not necessarily connected graph, the diversity vector of balls ($i$th component of the vector is equal to the number of different balls of radius i) is studied. Properties of metric balls in such graphs are established. In particular, a coincidence condition of balls with centers at different vertices is found. Based on these properties, the algorithm of computing the diversity vector of balls of a given graph $G=(V,E)$ with a running time $O(|V|^3)$ is developed.