Fibonacci-Like Sequences of Apollonian Circle Packings

Janet McShane and Michael Ratliff
Northern Arizona University

We consider an Apollonian Circle packing of the unit circle and illustrate a novel way to number the circles in the packing.  We then investigate several interesting properties of this circle packing including: a 4-color tiling of the plane; the fact that curvatures and Graham’s center*curvature coordinates satisfy Descartes equation; and the derivation of certain integer quadruples from the “polynomial” curvatures.

Certain subsequences of the circle packing  are studied and we investigate how those sequences depend on their so-called basis circles.  In one case, this dependence is typified by the emergence of Fibonacci number coefficients.  Finally, we generalize our results to a much wider class of circle packings.



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Janet M. McShane, PhD

Associate Professor

Department of Mathematics and Statistics

PO Box 5717

Northern Arizona University

Flagstaff, AZ 86011-5717

USA