Let A, B, and C be spheres that are tangent pairwise and whose points of tangency are distinct. Let {D₁, D₂, ..., D_n} be a set of spheres each of which is tangent to spheres A, B, and C. For i = 1 to n, D_i is externally tangent to D_i+1 (where D_n+1 = D₁).

What is the value of n?

(In reply to mathworld link by Jer)

>number of circles is not limited.

What do you mean by this?  that all the spheres above are circles instead?  only some?  Are the circles in 2- or 3-d space?

Posted by Josh70679 on 2005-11-04 17:13:01