On a Combinatorial Problem of Erdös and Hajnal
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In this note we consider some problems related to the following question: What is the smallest integer m(n) for which there exists a family Fn of sets A1, A2,…, Am(n) with the following properties, (i) each member of Fn has n elements and (ii) if S is a set which meets each member of Fn, then S contains at least one member of Fn? Erdős and Hajnal [1] observed that and that m(l) = 1, m(2) = 3, m(3) = 7.
[1] de Ng Dick Bruijn. A combinatorial problem , 1946 .
[2] Andras Hajnal,et al. On a property of families of sets , 1964 .