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Numbers n such that the radius of the smallest circle into which n unit circles can be packed is 1 + csc(Pi/k), where k >= 2 is an integer.

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`%I #7 Aug 13 2020 14:25:50
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`%S 2,3,4,5,6,7,8,9,11
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`%N Numbers n such that the radius of the smallest circle into which n unit circles can be packed is 1 + csc(Pi/k), where k >= 2 is an integer.
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`%C Corresponding k values are in A121604. For these n, the centers of k unit circles can form a regular k-gon with sides of length 2 centered at the center of the larger circle. From the diagrams in the link it appears likely that 13,18,19 are the next three terms.
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`%H E. Friedman, <a href="https://erich-friedman.github.io/packing/cirincir/">Erich's Packing Center: "Circles in Circles"</a>
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`%e See A121602 for the case n=11 involving a 9-gon.
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`%Y Cf. A121604, A121570, A121598, A121601, A121602.
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`%K nonn
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`%O 1,1
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`%A _Rick L. Shepherd_, Aug 09 2006
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