[thaumasiotes]

Prime factors are defined by a pretty rigid structure; you see a factor of 2 every two numbers; a factor of 3 every three numbers; a factor of 5 every five numbers...

[algorias]

For extra fun, if you plot the number of times a specific prime factor occurs, you get a fractal pattern. E.g. for the prime factor 2:

  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
  0  1  0  2  0  1  0  3  0  1  0  2  0  1  0