Among high-T-c superconductive copper oxides, there have been known phases that contain fluorite-structured layers as an additional "blocking block" between adjacent CuO2 planes. Here, we report that even a phase with the CuO2 planes separated by a 12-A thick quadruple-fluorite-layer block can be synthesized in a single phase and strongly oxygenated form to exhibit superconductivity with a T-c value as high as 55 K. The new phase is the fourth member of the (Cu,Mo)Sr-2(Ce,Y)(s)Cu2O5+2s+delta or (Cu,Mo)-12s2 homologous series. Comparison with the previously known s = 1, 2, and 3 members of the series reveals the amazing conclusion that T-c remains essentially unaffected upon inserting additional fluorite-structured layers between the two CuO2 planes as long as the hole-doping level of the planes is kept constant.