The theorem can be interpreted combinatorially in terms of partitions. In particular, the left hand side is a generating function for the number of partitions of "n" into an even number of distinct parts minus the number of partitions of "n" into an odd number of distinct parts. Each partition of "n" into an even number of distinct parts contributes +1 to the coefficient of "x""n"; each partition into an odd number of distinct parts contributes −1. (The article on unrestricted partition functions discusses this type of generating function.)