The M(4) problem of Erdos and Hajnal
The M(4) problem of Erdos and Hajnal
Isomorph-free exhaustive generation
Journal of Algorithms
Note: a new lower bound for the football pool problem for six matches
Journal of Combinatorial Theory Series A
Classification Algorithms for Codes and Designs (Algorithms and Computation in Mathematics)
Classification Algorithms for Codes and Designs (Algorithms and Computation in Mathematics)
Improving Bounds on the Football Pool Problem by Integer Programming and High-Throughput Computing
INFORMS Journal on Computing
Several new lower bounds on the size of codes with covering radius one
IEEE Transactions on Information Theory
On the size of optimal binary codes of length 9 and covering radius 1
IEEE Transactions on Information Theory
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A hypergraph is said to have property B if it is 2-colorable. Let m(k) denote the minimum number of edges in a k-uniform hypergraph that does not have property B. Erdos and Hajnal introduced the problem of determining m(k) in the early 1960s. The smallest cases, m(2)=3 and m(3)=7, are rather straightforward, but the next case has so far withstood all attacks; the possible values have been narrowed down to 21@?m(4)@?23. By an exhaustive computer search, it is here shown that m(4)=23.