Number Spirals are very simple. To make one, we just write the non-negative integers on a ribbon and roll it up with zero at the center. The trick is to arrange the spiral so all the perfect squares (1, 4, 9, 16, etc.) line up in a row on the right side. [...] It looks as though primes tend to concentrate in certain curves that swoop away to the northwest and southwest, like the curve marked by the blue arrow.

I like this kind of data visualization, it reminds me a comparison about different algorithms of pseudo random number generator and some periodicity found in visual patterns.