The (double) Primorial sieve  &  Prime spirals E-mail

The counterclockwise Ulam spiral (1963) with startvalue  0  is defined by  eight  families of functions.
These  eight  families of functions where discovered by placing the counterclockwise  Ulam spiral  with startvalue  0  in a Cartesian coordinate system.
Note: when using a different startvalue, this startvalue is added to each element.

The find made it possible to use  Excel  to further examine  the Ulam spiral.pdf,  while  (large) computer programs  can use the same principles.


The Ulam spiral: Using the Cartesian coordinate system