If you're plotting primes, all the coordinates where you're not plotting are non-prime - so every 2nd coordinate will be blank. As will every 3rd and every 4th, 5th, 10th, 11th. etc etc.
I’m not a mathematician so correct me if I’m wrong, but the patterns that emerge or more the natural result of the plotting method vs revealing anything meaningful about the distribution of primes.
Not a mathematician either but I think some quadratics have a tendency to produce more primes than others. What you are seing is the characteristic of various quadratics when plotted in this way. I plotted something quite simmilar.
> So what’s clear here is that the spirals themselves have nothing to do with prime numbers; a much cleaner and fuller pattern can be seen when we plot all positive integers (as well as zero).
https://en.wikipedia.org/wiki/Ulam_spiral
Why do prime numbers make these spirals? | Dirichlet’s theorem and pi approximations - 3Blue1Brown
https://www.youtube.com/watch?v=EK32jo7i5LQ