The natural numbers are arranged in a counter-clockwise spiral, starting with 1 at the white spot in the center: 5 4 3 6 1 2 7 8 9 ... Multiples of 2 are colored red, 3 orange, 5 yellow, 7 light green, 11 green, ... You get the idea. Prime numbers are black. Do you see any patterns? Increase the number of turns to spiral out to larger numbers, and press <space> to recalculate. (Turbo mode <shift><flag> recommended for large n.)
