Charming story -- but there's plenty of controversy that comes with it. Some Canadian mathematicians ran their own analysis in 2014 and published it in Chance magazine, arguing that Johnson's winning prospects weren't nearly good enough under the terms described for him to have been likely to have achieved such scores. The full article is behind a $48 paywall, but here's a link to the start of it: http://www.tandfonline.com/doi/abs/10.1080/09332480.2014.890...
Meanwhile, Elliot Jacobson, a guy with his own academic pedigree (U of Arizona Ph.D. in math; former Ohio University asst/assocmath professor) has published a defense of Johnson's claims and a counter-rebuttal to the Canadians. Jacobson now runs a gambling-consulting firm. His rebuttal is here: http://apheat.net/2014/03/25/fact-checking-an-article-on-don...
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