Lexicographic replacement can destroy two-intersection
ID: lexicographic-replacement-can-destroy-two-intersection
On eight points, the rank-four Frankl family consisting of sets containing at least three of has seventeen members and is two-intersecting. The first fifteen rank-four sets in lexicographic order contain , while the sixteenth is . The earlier set meets it only at one. This disproves preservation of two-intersection by lexicographic replacement even when the rank is half the ground-set size.
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