Configurations with Subset Restrictions
نویسندگان
چکیده
closed families of sets. Poonen showed that if a finite union-closed family of sets S contains three of the 3−sets in some 4−set, then one of the elements of that 4−set is contained in at least half the members of the family S. This condition intrigued us, and we began to investigate collections of 3−sets for which it fails. The alternative statement that no 4−set contain more than two 3−sets in the
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