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Solution to Math Problem Begins in Unexpected Place

Newser — John Johnson

It might be the strangest journey to the solution of a math conundrum ever. It turns out that an anonymous post on the online forum 4chan about how to watch a Japanese anime series may have helped crack a 25-year-old math problem, reports the Verge.

Not surprisingly, this one takes some unpacking, and it starts here: In September 2011, a fan of the series The Melancholy of Haruhi Suzumiya posted a question on 4chan about the 14-episode first season.

The season deals with time travel, and the episodes did not air in chronological order, a quirk that prompted a debate among fans about the best order in which to watch them.

The question that went up on 4chan: If someone wanted to watch them in every possible order, what's the minimum number they'd have to watch? The answer soon came from an anonymous poster: 93,884,313,611, per Quanta Magazine.



“Please look over [the proof] for any loopholes I might have missed,” wrote the poster, but his solution languished in obscurity for seven years. What mathematicians have just discovered is that the proof is not only legit but an important advance in a problem first raised in 1993 in the field of combinatorics and involving "superpermutations." The post didn't provide a complete solution, but last month, sci-fi writer Greg Egan seemed to solve another key part—in math lingo, he provided the "upper bound" answer to the 4chan poster's "lower bound" answer.

It was Egan's post that drew new attention to the 4chan post. Now mathematicians are working to combine the two into one solution. “It’s a weird situation that this very elegant proof of something that wasn’t previously known was posted in such an unlikely place,” says one.

(This solution to a $1 million math problem isn't going over well.)

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