Apologies for the vagueness of the question, I'll clean it up once an answer helps me describe it better.
I'm fascinated by the pattern demonstrated in this image. It's made up of dots on a series of concentric circles. The angles used, number of dots on each circle and circle sizes cause a spiral pattern to emerge.
Is there a name for this or a combination of principles at play here? I'm interested in the mathematics of it, and how such an image might be defined in equations.
Image credit: the talented fellow at http://dotboydesigns.vpweb.com.au
(I no longer think this is accurate; see the second paragraph.) The consecutive dots are rotated by the golden angle, which is $(1 - 1/\phi)$th of a whole turn, where $\phi = (1 + \sqrt 5)/2$ is the golden ratio. There's a nice interactive demonstration, as well as an explanation of how this works to create beautiful spirals, on this page: http://www.mathsisfun.com/numbers/nature-golden-ratio-fibonacci.html ...The essential reason is that the golden ratio is very poorly approximated by rational numbers, so no single spiral arises that can dominate the whole pattern.
Edit: I don't think the image in the question actually uses the golden angle. It's just lots of alternating dots in concentric circles, with some artistically chosen spreading of their radii. However, you can generate some very beautiful and very similar-looking spirals, without requiring any artistic selection, using the principles I described above.