%I #7 Aug 13 2020 14:25:50

%S 2,3,4,5,6,7,8,9,11

%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.

%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.

%H E. Friedman, <a href="https://erich-friedman.github.io/packing/cirincir/">Erich's Packing Center: "Circles in Circles"</a>

%e See A121602 for the case n=11 involving a 9-gon.

%Y Cf. A121604, A121570, A121598, A121601, A121602.

%K nonn

%O 1,1

%A _Rick L. Shepherd_, Aug 09 2006