"Hamamura Nagisa no Keisan Nooto" (Hamamura Nagisa's Calculation Notes) volume 6 by Aoyagi Aito. This volume includes large prime numbers and small fractions.
When we hear "large prime numbers", the first thing that comes to mind is probably the Mersenne prime numbers, the search for those are still going. The first chapter had a more dramatized version of this search, where a group of women continued their pursue of prime numbers in a secluded monastery. Note that Mersenne primes aren't the only large primes, there are also others such as Cullen primes, and this novel managed to build a whole murder plot around these series, with a punchline that involves an otherwise wholly ordinary three digit number. It wasn't quite the same impact as "42" in Hitchhiker's Guide to the Galaxy, but it definitely made a memorable scene.
The ordinary bits are carried even further in the last chapter, which is based on the Rhind Mathematical Papyrus. This chapter took the first part of the Rhind Papyrus and illustrated with lively detail, explaining why the solution to 4 divided by 5 made more sense as 1/2 + 1/4 + 1/20, as opposed to simply 4/5. Unfamiliar conventions like these was part of the reason why I did not spend too much time reading the Rhind Papyrus, but this chapter did a great job in explaining the details and rationales, and connecting it all to people's daily lives. This aspect of giving new life to abstruse subjects is what makes this novel series so great.
The middle chapters include Napoleon's theorem and De Morgan's laws, plus a bit of Cantor's countable sets. One part of the dialog best captures the essence of these terrorists:
"I think there are more reliable ways to kill someone."
"Fools! It's the great honorable theorem found by Napoleon! It wouldn't be right to not use it!"
The overarching plot of dealing with the terrorists did not progress much, but that doesn't bother me at all. It has been another volume with fine balance between new math topics and quirky characters, looking forward to see more topics getting the Nagisa treatment.
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