# Apollonian Edge Circles

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The curvature (or bend) of a circle of radius is .

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Contributed by: Ed Pegg Jr (April 2020)

Open content licensed under CC BY-NC-SA

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References

[1] E. Pegg Jr. "The Circles of Descartes" from the Wolfram Demonstrations Project—A Wolfram Web Resource. demonstrations.wolfram.com/TheCirclesOfDescartes.

[2] OEIS, A004613, Numbers that are divisible only by primes congruent to 1 mod 4.

[3] J. C. Lagarias, C. L. Mallows and A. R. Wilks, "Beyond the Descartes Circle Theorem." arxiv.org/abs/math/0101066.

[4] D. Austin. "When Kissing Involves Trigonometry." American Mathematical Society, March 2006. www.ams.org/featurecolumn/archive/kissing.html.

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