Time evolution of the surface density of solids for small planetesimals at the Jupiter-Saturn region for a disk with a power index p = 3/2, considering the case of the simultaneous formation and employing a distribution of planetesimals between and  km. After 0.5 Myr. the surface density of solids at Jupiter’s neighborhood is significantly augmented by the incoming flow of planetesimals owing to the gravitational perturbations of the outer planets (color figure only available in the electronic version).