As of Apr. 2019, this entry is now moved to the 'Deprecated' section.
This theorem is widely regarded as having been solved.
See : Formal Proof—The Four-Color Theorem Notices of the AMS Volume 55, Number 11.
For reference, the original text of the article is archived below :
The Four Color Theorem states that given any separation of a plane into contiguous regions, producing a figure called a map, no more than four colors are required to color the regions of the map so that no two adjacent regions have the same color. Source : Wikipedia
Computational tests, checking millions of possible configurations, have never found an exception. (note that a formal proof with 5 colors was made in the late 19th century by Percy Heawood, seeWikipedia ).
A 'machine generated proof' was described by Georges Gonthier of Microsoft Research Cambridge England, in 2007. See: Asian Symposium on Computer Mathematics, ASCM 2007 Asian Symposium on Computer Mathematics, ASCM 2007: Computer Mathematics pp 333-333
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