Sci-Fi Writer Greg Egan and 4chan anon Math Whiz Advance Permutation Problem | Quanta Magazine

mathematics
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permutation
proofs

5 weeks ago by jm

On September 16, 2011, an anime fan posted a math question to the online bulletin board 4chan about the cult classic television series 'The Melancholy of Haruhi Suzumiya'. Season one of the show, which involves time travel, had originally aired in non-chronological order, and a re-broadcast and a DVD version had each further rearranged the episodes. Fans were arguing online about the best order to watch the episodes, and the 4chan poster wondered: If viewers wanted to see the series in every possible order, what is the shortest list of episodes they’d have to watch?

In less than an hour, an anonymous person offered an answer — not a complete solution, but a lower bound on the number of episodes required. The argument, which covered series with any number of episodes, showed that for the 14-episode first season of Haruhi, viewers would have to watch at least 93,884,313,611 episodes to see all possible orderings. “Please look over [the proof] for any loopholes I might have missed,” the anonymous poster wrote.

The proof slipped under the radar of the mathematics community for seven years — apparently only one professional mathematician spotted it at the time, and he didn’t check it carefully. But in a plot twist last month, the Australian science fiction novelist Greg Egan proved a new upper bound on the number of episodes required. Egan’s discovery renewed interest in the problem and drew attention to the lower bound posted anonymously in 2011. Both proofs are now being hailed as significant advances on a puzzle mathematicians have been studying for at least 25 years.

5 weeks ago by jm

Random with care

january 2018 by jm

Some tips about RNGs and their usage

(via Tony Finch)

coding
random
math
rngs
prngs
statistics
distributions
(via Tony Finch)

january 2018 by jm

'Mathwashing,' Facebook and the zeitgeist of data worship

maths
math
mathwashing
data
big-data
algorithms
machine-learning
bias
facebook
fred-benenson

april 2017 by jm

Fred Benenson: Mathwashing can be thought of using math terms (algorithm, model, etc.) to paper over a more subjective reality. For example, a lot of people believed Facebook was using an unbiased algorithm to determine its trending topics, even if Facebook had previously admitted that humans were involved in the process.

april 2017 by jm

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