The 2/3/5/7-smooth integers on a generalized Ulam spiral [Les entiers 2/3/5/7-friables sur une spirale d'Ulam généralisée].
Starting from the center of the picture, the spheres are
numbered (N=2,..., 16130) when following a
square spiral. The radius of the sphere displaying the number N is proportional
to the square root of the smoothness K of N (K being the largest prime factors of N).
Nota: The 2/3/5/7-smooth numbers are coded using respectively the following colors: {red,green,orange,white}.
The other numbers are dark blue.
