Fed up with Sudoku? Try Quadron and discover the famous 4 colours theorem! 2970 levels, hours of entertainment.
The 4 colours conjecture was first proposed in 1852 when Francis Guthrie, while trying to color the map of countries of England, noticed that only four different colors were needed. It has been notorious for attracting a large number of false proofs and disproofs in its long history.
It was proven in 1976 by Kenneth Appel and Wolfgang Haken. It was the first major theorem to be proved using a computer.
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