Numerical results for the scattering cross section (S) ofN=3–26 equally spaced monopole resonators on a circle (of radiusb) indicate regularities in the values of the normalized diameter (2kb=4πb/λ=ρwith λ as the wavelength) corresponding to maximal scattering for symmetrical excitation. The peaksS∧(N)occur forρ=ρ∧(N)betweenNand 2N, i.e., for circle circumference betweenNλ/2 andNλ. With increasingN, the values ofρ∧(N)in successive alternating sets (shells) of three or four values ofNare close toρm=2mπ−π/4;shell-1 consists ofN=3–5, shell-2 ofN=6–9, shell-3 ofN=10–12, etc. The basis for the shell structure is delineated by a simple asymptotic approximation (for large ρ andNin the range ρ<2N) or a cylindrical wave representation for a sum of spherical waves. A simple approximation is also derived fo the shift in resonance frequency that occurs for ρ small enough for the array to respond as a collective monopole.