Partitions with multiplicity constraints
摘要
This paper explores two families of integer partition functions, Q(d; n) and P(d; n), which count partitions of n under certain restrictions on how many times each part can appear. The first function, Q(d; n), counts partitions where no part shows up d or more times. The second, P(d; n), involves a signed count of partitions where the number of times each part appears is either 0 or 1 modulo d. These functions generalize some well-known partition types—like distinct partitions—and turn out to have a surprisingly rich structure. We prove a collection of identities that tie these two functions together. This includes convolution formulas, mutual expansions, and an orthogonality relation. We also find recurrences and develop exact formulas for both Q(d; n) and P(d; n) using sums over partitions. Altogether, these results reveal a deeper algebraic and combinatorial picture behind partitions with multiplicity constraints.