The Wiener number of the hexagonal net

The Wiener number of a molecular graph, or more generally of a connected graph, is equal to the sum of distances between all pairs of its vertices. A graph formed by a hexagon in the centre, surrounded by n rings of hexagonal cells, is called an n-hexagonal net. It is shown that the Wiener number of an n-hexagonal net equals 15(164n5 − 30n3 + n).