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Results tagged with co.combinatorics
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user 85122
Enumerative combinatorics, graph theory, order theory, posets, matroids, designs and other discrete structures. It also includes algebraic, analytic and probabilistic combinatorics.
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Difficult examples for Frankl's union-closed conjecture
Here is a generalisation, quite a strong one :
Let $E$ be a finite set $F\subset \mathcal P(E)$, such that $\emptyset\notin F$, $E\in F$, and $F$ closed for union.
Let $f(F)=\left\{x\in E| |F_x|<|F …