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Four color theorem
The four color theorem says, that it is possible to color a map with only four colors in such a way that no two adjacent countries are the same color.
Explanation
The theorem holds only if the countries each form a whole, and lie on a surface topologically equivalent to a flat plane or a sphere.
Five countries with their graph structure
The problem was reduced to 1,936 specific cases, and these were then all computed by a computer. In doing so, they provided the first computer-assisted proof in mathematics - a milestone that led to much discussion at the time.
HistoryThe four-color theorem was proved in 1976 by Kenneth Appel and Wolfgang Haken. |