AVirtualMachineForExploringSpaceTimeAndBeyond : The 2/3/5/7/11/13/17-smooth integers on a generalized Ulam spiral (Les entiers 2/3/5/7/11/13/17-friables sur une spirale d'Ulam generalisee).

The 2/3/5/7/11/13/17-smooth integers on a generalized Ulam spiral [Les entiers 2/3/5/7/11/13/17-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 2/3/5/7/11/13/17-smooth numbers are coded using respectively the following colors: {red,magenta,green,cyan,yellow,orange,white}. The other numbers are dark blue.

[Plus d'informations à propos de la spirale d'Ulam et de ses généralisations -en français/in french-]
[More information about the Ulam spiral and ist generalizations -in english/en anglais-]

See some related pictures (including this one):