What is the minimum number of pennies that can be placed upon a table so that each penny touches three, and only three, others?

(All the pennies must lie flat on the table.)

(In reply to solution by SilverKnight)

I tried to verify SK's solution using actual pennies on an actual table, and it works beautifully. Intuitively it seems that 16 is the minimum number.

Posted by Penny on 2003-12-17 16:28:48