If you imagine a 5x1 rectangular array of spheres centered above and lying upon a 4x2 rectangular array of spheres, likewise upon a 3x3, likewise upon a 2x4, likewise upon a 1x5 . . . then you see how a tetrahedral array of spheres can also be thought of as layers of square arrays of spheres each nestled in the hollows of the one below it. --Dan On 2013-06-21, at 3:43 AM, Bill Gosper wrote:
I asked Neil if Kepler's sphere-stacking conjecture was about tetrahedral or square pyramids of cannonballs. He fooled with Mathematica briefly and said it doesn't matter <http://gosper.org/kepvor.png>. --rwg _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun