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The Ulam Spiral

… and many other spirals 
inspired by it …

Pentapolar
Ulam-Type Spiral

Spiral origin at 0.

Spiral origin color-coded as a 6-fold.

“1” represented on spiral.
(Adjacent to 0, 0 is a  6-fold.)

“2” & “3” not represented on spiral.
(Not adjacent to a 6-fold.)

 

Color-coded number-groups:
click below for show/no-show settings.

display control

6-folds

prime adjacents

composite adjacents

Spiral features:
click below for show/no-show settings.

display control

Empty Locations

Spiral

Sector Lines

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pentapolar-spiral-layer2
pentapolar-spiral-layer3
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pentapolar-spiral-empty
pentapolar-spiral-spiral
pentapolar-spiral-sector-lines