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

The segmented prime spirals are an offspring of the Ulam spiral.
The counterclockwise Ulam spiral with startvalue  0  is a  four-quarter spiral,  and thus a prime spiral with four segments. There are infinitely many segmented prime spirals.

In the picture above is a Ulam five-quarter spiral, and thus a prime spiral with five segments. Clearly visible is the translation  n   to  n - 1  at the seam.

Below shows of a prime spiral with six segments.
The last picture is a hexagram representation of a continuous prime spiral with six segments, very simular to the hexagram of a prime spiral with three segements.


Prime spirals: Prime spiral with more segments (with  more > 4).