Abstract. We introduce two new integer partition functions, both of which are the number of partition quadruples of n with certain size restrictions. We prove both functions satisfy Ramanujan-type congruences modulo 3, 5, 7, and 13 by use of generalized Lambert series identities and q-series techniques.
IntroductionWe recall a partition of a positive integer n is a non-increasing sequence of positive integers that sum to n. For example, the partitions of 5 are 5, 4 + 1, 3 + 2, 3 + 1 + 1, 2 + 2 + 1, 2 + 1 + 1 + 1, 1 + 1 + 1 + 1 + 1. We let p(n) denote the number of partitions of n. The function p(n) satisfies the well known congruences of Ramanujan p(5n + 4) ≡ 0 (mod 5), p(7n + 5) ≡ 0 (mod 7), and p(11n + 6) ≡ 0 (mod 11). In this article we will consider two partition quadruples of n. We say a quadruple (π 1 , π 2 , π 3 , π 4 ) of partitions is a partition quadruple of n is altogether the parts of π 1 , π 2 , π 3 , and π 4 sum to n.For a partition π, we let s(π) denote the smallest part of π and ℓ(π) denote the largest part of π. We use the conventions that the empty partition has smallest part ∞ and largest part 0. We let u(n) denote the number of partition quadruples (π 1 , π 2 , π 3 , π 4 ) of n such that π 1 is non-empty,, and ℓ(π 4 ) ≤ 2s(π 1 ). We let v(n) denote the number of partition quadruples (π 1 , π 2 , π 3 , π 4 ) of n such that the smallest part of π 1 appears at least twice, s(π 1 ) ≤ s(π 2 ), s(π 1 ) ≤ s(π 3 ), s(π 1 ) ≤ s(π 4 ), and ℓ(π 4 ) ≤ 2s(π 1 ).We use the standard product notation,By summing according to n being the smallest part of a partition, one easily deduces that a generating function for p(n) is given bySimilarly, by summing according to n being the smallest part of the partition π 1 , we find that generating functions for u(n) and v(n) are given by(q n ; q) ∞ (q n ; q) ∞ (q n ; q) ∞ (q n ; q) n+1 .The main result of this article are the following congruences for u(n) and v(n).