It wasn't exactly clear to me when I read the article, so here's my explanation: - take a line of integers, color them black if prime, red otherwise - hexagon

It wasn't exactly clear to me when I read the article, so here's my explanation: - take a line of integers, color them black if prime, red otherwise - hexagonally arrange them in a spiral (similar to Ulam's spiral) - cut the hexagon into six equilateral triangles - overlap the triangles (rotate where necessary) - if any pixels are black, color the whole thing black, if none are black, color it red - interesting pattern arises - interesting pattern already exists as per http://oeis.org/A054521 http://oeis.org/A054521 Edit: They may be packing more than 6 numbers into a pixel, looks like 75. Unsure how that would look visually, but you extend the above to use 75 or any other number. Unsure why 75 was chosen, maybe it's the only interesting one?