I've forgotten where I saw this---perhaps it was a Project Euler problem. In any case, you can see the pattern. It's a nice (fairly simple) exercise in Python to construct a list of lists and the functions to modify it. The great thing is that once you have the inner 3 x 3 circle correct, the rest is automatic. The code for this is in
The real reason I'm posting about it is that it makes a fun plotting project for
matplotlib, especially in combination with the prime number generator that we worked up the other day (in
The graphic at the top of the post was obtained by modifying the array to hold n % 10 for each value, and using the matplotlib color map called "winter." I think for that one I had n = 50, so that's a 101 x 101 grid.
The prime example :) has n = 40 and uses the 'autumn' colormap. That's the one that
script.pyis set up to generate at the moment. Is there a pattern or is it just random?
[UPDATE: I did a bit of testing. In tracing the results for the prime plot using a small n, I discovered that
matplotlibhas shown the matrix in a different way than I printed it at the top of the post. Their "heatmap" goes vertically for the first step and cycles clockwise; it is both a mirror image and rotated 180 degrees from the way I did it. Sorry. But, now that I'm done, I think I can just leave it that way... ]
Zipped project files on Dropbox (here).