Prime Spirals

Alex Bellos discusses how the Incans used knots in string (Quipu) to record numbers.Check out Brilliant (get 20% off their premium service): https://brillian...

Prime numbers, Ulam Spirals and other cool numbery stuff with Dr James Grime.

James Clewett on spirals at: http://youtu.be/3K-12i0jclM

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And "golden line" in this context was made up by Brady!