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

The counterclockwise Ulam spiral (1963) with startvalue  0  is defined by  eight  families of functions. With these families of functions  ANY  area of the spiral can be examined, without building the spiral from the ground up  (see above).

Excel can be used to further examine the Ulam spiral using just the  four  functions of the North, East, South and West sector. The  Excel sheet   contains examples of how to use these functions, even with different startvalues.
These same principles (based on a Cartesian coordinate system) can be used in any (large) computer program.


The Ulam spiral: The build using the eight families of funtions