A more interesting picture would be one where all of the even numbers are omitted. I made canvas renderer to check it: http://alteredqualia.com/visualization/

A more interesting picture would be one where all of the even numbers are omitted. I made canvas renderer to check it: http://alteredqualia.com/visualization/ulam-spiral.html http://alteredqualia.com/visualization/ulam-spiral.html It's not checkerboard, but there are horizontal and vertical patterns.