Nuclear mass relations based on systematics of proton-neutron interactions

The proton-neutron interaction between the last proton and the last two neutrons, V_1p-2n, and that between the last two protons and the last neutron, V_2p-1n, for nuclei with mass number A60, are extracted by using experimental binding energies of neighboring nuclei. By using a simple function to describe V_1p-2n and V_2p-1n, we present new relations connecting the masses of neighboring nuclei with improved accuracies.