**Percy John Heawood** (1861-1955) was a British mathematician. He devoted essentially his whole working life to the four colour theorem, a result which he was the first to state explicitly in 1890. It was finally proved in 1976. 1861 is a common year starting on Tuesday. ...
1955 (MCMLV) was a common year starting on Saturday of the Gregorian calendar. ...
Example of a four color map The four color theorem states that every possible geographical map can be colored with at most four colors in such a way that no two adjacent regions receive the same colour. ...
1890 was a common year starting on Wednesday (see link for calendar). ...
## See also The Heawood conjecture in graph theory was an expected formula to give the correct upper bound for the number of colors which are sufficient for graph coloring on a surface of a given genus. ...
The Heawood graph, of girth 6 In the mathematical field of graph theory, a Heawood graph is the 6-cage, the smallest cubic graph of girth 6. ...
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