The (double) Primorial sieve & Prime spirals |
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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).