[seqfan] Number of touching points between unit circles in the optimal packing of circles in a circle

Felix Fröhlich felix.froe at gmail.com
Sun Mar 19 10:48:14 CET 2017

Dear Sequence Fans,

Let A be an arrangement of n unit circles in the plane, let r the radius of
the smallest circle that can enclose A and let t be the number of points
where two unit circles in the arrangement touch each other.

A sequence arising from the above is the following:

a(n) = the value of t for the specific A such that r is minimal over all
possible A.

https://en.wikipedia.org/wiki/Circle_packing_in_a_circle seems to suggest
that the sequence with offset 2 starts

1, 3, 4, 5, 6, 12, 7, 8, 12, 14

This is not in the OEIS. Are the terms correct and should this be in the

Best regards
Felix Fröhlich


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