Portal:Mathematics/Featured picture/2010 11
Picture of the month
Credit: David Eppstein
In geometric graph theory, the Hadwiger–Nelson problem, named after Hugo Hadwiger and Edward Nelson, asks for the minimum number of colors required to color the plane such that no two points at distance one from each other have the same color. The answer is unknown, but has been narrowed down to one of the numbers 4, 5, 6 or 7.
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