the reciprocal degree distance (rdd), defined for a connected graph $g$ as vertex-degree-weighted sum of the reciprocal distances, that is, $rdd(g) =sumlimits_{u,vin v(g)}frac{d_g(u) + d_g(v)}{d_g(u,v)}.$ the reciprocal degree distance is a weight version of the harary index, just as the degree distance is a weight version of the wiener index. in this paper, we present exact formu...