  The neutron and proton odd-even mass differences are studied with
Hartree-Fock+BCS (HFBCS) calculations with Skyrme interactions and an isospin
dependent contact pairing interaction, which is recently derived from a
microscopic nucleon-nucleon interaction. To this end, we perform HFBCS
calculations for even and odd semi-magic Tin and Lead isotopes together with
even and odd Z isotones with $N$= 50 and 82. The filling approximation is
applied to the last unoccupied particle in odd nuclei. Comparisons with the
experimental data show a clear manifestation of the isospin dependent pairing
correlations in both proton and neutron pairing gaps.
