A great time waster is this web site:

http://www.numberspiral.com/

for generating spirals rich in prime numbers.

Now, when primes are plotted on a 1-D array, ie., a number line, no
patterns emerge. However, wehn we plot them on a 2-D array we see the
sorts of patters seen on these spirals and on the Ulam spiral. What
happens if we find a way to plot them on a 3-D array?