There are only three pairs of Brown Numbers – and only five of the numbers themselves (because 5 is repeated)… At least we think that’s all of them? No-one has proven it. This is called Brocard’s Problem and has been entertained by great mathematicians such as Paul Erdos.
The Brown Numbers are (5,4) (11,5) and (71,7).
Professor Ed Copeland works at the University of Nottingham. He also features in our Sixty Symbols physics videos at http://www.youtube.com/sixtysymbols — https://twitter.com/ProfEdCopeland
Brown Paper Blog Post: http://periodicvideos.blogspot.co.uk/2012/02/brown-paper-question.html
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