August 2007 - mathfun@mailman.xmission.com

[math-fun] John R. Hendricks (1929-2007)
by Christian Boyer 03 Aug '07

03 Aug '07

It is with sorrow that I report to you the passing of John R. Hendricks, on July 7, 2007. He was known for his works on magic hypercubes ("tesseracts"), for his bimagic cube of order 25 www.multimagie.com/English/Cube.htm, and for his numerous papers published in the Journal of Recreational Mathematics. In 2003, I was pleased to dedicate him the first known bimagic hypercubes: www.multimagie.com/English/Hypercubes.htm A biographical sketch: www.multimagie.com/English/Hendricks.htm Another bio published in the JRM, 20 years ago: www.multimagie.com/English/HendricksJRM.htm Christian.

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[math-fun] Sphere puzzle
by Dan Asimov 02 Aug '07

02 Aug '07

Define a sequence of unit spheres in 3-space as follows: Let spheres S_1, S_2, S_3, S_4 be mutually tangent. Given S_k with k >= 4, define S_(k+1) as the unique unit sphere that's tangent to S_k, S_(k-1), S_(k-2) but is unequal to S_(k-3). Puzzle: Do all spheres S_k have disjoint interiors? Prove your answer. Please submit answers to me rather than math-fun: dasimov at earthlink.net . I'll post them to math-fun in a couple of days. --Dan

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[math-fun] looking for review of computation costs
by Richard Schroeppel 01 Aug '07

01 Aug '07

I'm looking for a hypothetical review article that I hope someone has written for me: It contains a summary of computing costs for various optimal algorithms ... Multiplying complex numbers takes 3 real multiplications. Multiplying quaternions takes 7 real multiplications. etc. Rich

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