Intersecting integer partitions
نویسنده
چکیده
If a1, a2, . . . , ak and n are positive integers such that n = a1+a2+· · ·+ak, then the sum a1 + a2 + · · ·+ ak is said to be a partition of n of length k, and a1, a2, . . . , ak are said to be the parts of the partition. Two partitions that differ only in the order of their parts are considered to be the same partition. Let Pn be the set of partitions of n, and let Pn,k be the set of partitions of n of length k. We say that two partitions t-intersect if they have at least t common parts (not necessarily distinct). We call a set A of partitions t-intersecting if every two partitions in A t-intersect. For a set A of partitions, let A(t) be the set of partitions in A that have at least t parts equal to 1. We conjecture that for n ≥ t, Pn(t) is a largest t-intersecting subset of Pn. We show that for k > t, Pn,k(t) is a largest t-intersecting subset of Pn,k if n ≤ 2k − t + 1 or n ≥ 3tk. We also demonstrate that for every t ≥ 1, there exist n and k such that t < k < n and Pn,k(t) is not a largest t-intersecting subset of Pn,k.
منابع مشابه
Strongly intersecting integer partitions
We call a sum a1 + a2 + · · ·+ ak a partition of n of length k if a1, a2, . . . , ak and n are positive integers such that a1 ≤ a2 ≤ · · · ≤ ak and n = a1 + a2 + · · ·+ ak. For i = 1, 2, . . . , k, we call ai the i-th part of the sum a1 + a2 + · · ·+ ak. Let Pn,k be the set of all partitions of n of length k. We say that two partitions a1 + a2 + · · · + ak and b1 + b2 + · · ·+ bk strongly inter...
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ورودعنوان ژورنال:
- Australasian J. Combinatorics
دوره 66 شماره
صفحات -
تاریخ انتشار 2016