We have studied the stability and the structure of doped noble gas cluster ions of the type M+Xn, (M=In, Al, Na, X=Ar, Kr, Xe) by systematically changing the composition M/X and observing changes in the magic number patterns appearing in the mass spectra. When the metal ion radius is comparable to the radius of the noble gas atom, the mass spectra show the familar icosahedral magic numbers n+ 1=13,19,23,26,29,32, 46, 55,... In constrast, for metal ions with radii significantly smaller than the noble gas atoms, we observe a new series of magic numbers n + 9, 11, 17, 21,24, 26,... This series converts into the icosahedral one for larger clusters. Using a simple hard sphere packing model, we show that this new series of magic numbers is consistent with a cluster growth sequence which is based on a capped square antiprism (CSA) geometrical structure of the clusters.