Patterns obtained by successively laying down circles in such a way
that the center of each new circle is as close as possible to the
center of the first circle. The extent to which these represent the
densest possible packings is not clear, and indeed it is quite
possible that in most such actual packings circles of different sizes
are just separated into several uniform regions.
[From A New Kind of Science, page 350.]
© 2002 by Stephen Wolfram,