[en] Using spin projection operator methods, generating functions are developed for nuclear spin species. These operators also generate elegantly the irreducible respresentations spanned by a₁/sup b/₁ a₂/sup b/₂xxxa/sub t//sup b//sub t/ nuclear spin functions, where a/sub i/ is the number of possible spin states of the b/sub i/ nuclei of the same kind in the molecule. From these generating functions the statistical weights of the rovibronic levels of any polyatomic molecule can be obtained easily. The method is illustrated with ³³SF₆, ¹³C-triphenylene, and triphenylene with protons replaced by D. For ¹³C-triphenylene there are 1 073 741 824 nuclear spin functions from which we determined the statistical weights of the rovibronic levels A/sup prime/₁, A/sup prime/₂, E', A/sup double-prime/₁, A/sup double-prime/₂, and E'' to be 178 940 928, 178 973 696, 357 913 600, 178 940 928, 178 973 696, and 357 913 600, respectively