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Colin the Mathmo

@andrewt From Gareth McCaughan.

The average number of ways to express numbers from 1 to N
as sums of two squares

=

(total number of ways to express numbers from 1 to N as X2+Y2 )/N

=

(total number of (x,y) for which 0<x2+y2<=N )/N

=

(total number of (x,y) inside the circle
X2+Y2=N, minus 1)/N

=

(area inside the circle X2+Y2=N + O(N) ) /N

=

(area inside the circle X2+Y2=N2, +O(N)) /N

= πN2+O(N))/N

= π+O(1/N)

@andrewt It is - I agree entirely. One could probably make some nice visualisations of that happening, and there are less formal (but effectively identical) arguments.

But yes, lovely.

@ColinTheMathmo I had to draw some stuff to properly get my head around it but yes, with the visuals and some handwaving it's very intuitive.

Perfect MathsJam talk material.

@andrewt Indeed - a lovely opening hook, and once seen, a clear intuition as to why it's true.

@andrewt Have you submitted your talk for MathsJam yet?

@ColinTheMathmo oh, I have not, I quite forgot. That can go on tonight's list, right after "clean kitchen"