From dik@cwi.nl Sun Jun 13 19:53:20 1993 Return-Path: Received: from charon.cwi.nl by life.ai.mit.edu (4.1/AI-4.10) for /com/archive/cube-lovers id AA19146; Sun, 13 Jun 93 19:53:20 EDT Received: from boring.cwi.nl by charon.cwi.nl with SMTP id AA25903 (5.65b/3.8/CWI-Amsterdam); Mon, 14 Jun 1993 01:53:19 +0200 Received: by boring.cwi.nl id AA19557 (4.1/2.10/CWI-Amsterdam); Mon, 14 Jun 93 01:53:16 +0200 Date: Mon, 14 Jun 93 01:53:16 +0200 From: Dik.Winter@cwi.nl Message-Id: <9306132353.AA19557.dik@boring.cwi.nl> To: cube-lovers@life.ai.mit.edu Subject: Contents of CFF31 Last Friday I received issue #31 of Cubism For Fun. A short summary of the contents: 1. Short articles by Jan de Geus and Frans de Vreugd about Cube Day 1992. 2. An article by Herbert Kociemba about a classification of pretty patterns on the cube. 3. Reflections by Tom Verhoeff about puzzles and computers. 4. Announcement by Koos Verhoef and Tom Verhoeff of a contest *. 5. A short article by Jaques Haubrich about Rubik's Tangle and how to position 24 parts in a cube like way (four on a side). 6. An article by Jan Verbakel about the creation of castles with solid pentominoes. 7. A short article by Trevor Wood on the pecking of octacubes. 8. A short article by Jaques Haubrich about a difficult packing problem. 9. An article by David Singmaster about a gathering in Atlanta in honor of Martin Gardner. (Nearly the whole puzzling world appears to have been there.) 10. A new contest by Anton Hanegraaf. 11. Announcement of the 13th Dutch cube day on August 22 in Amsterdam. This day is next to the 13th International Puzzle Party. * This is an interesting puzzle indeed. Consider the densest sphere packing in 3D. This is the packing where you start with a lattice of spheres based on a triangular lattice, and put on top of it another, similar, lattice such that each sphere of the new layer fits in a hole in the lower layer. Add more layers. Pick from that all possible configurations of 4 connected spheres. There are 25 such configurations. The puzzle is to create from these 25 pieces a pyramid with a side of 8 spheres (which contains 120 spheres), with a hole at the center that consists of a pyramid with a side of 4 spheres (remember those sums of triangular numbers!). It is not known whether there is a solution. The authors tell how they have a TRS-80 now running 5 years on this problem, using backtracking techniques. Until now the first 6 pieces did not move. The could fit 24 pieces already 521,010 times. The puzzle was first announced at the previous Cube Day. CFF is a newsletter published by the Nederlandse Kubus Club NKC (Dutch Cubists Club). It appears a bit irregular, but a few times a year. Yearly membership fee is now NLG 25.- (Dutch Guilders) which amounts to approximately $ 15.-. Information: Anton Hanegraaf Heemskerkstraat 9 6662 AL Elst The Netherlands (sorry, there is no e-mail address). -- dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland home: bovenover 215, 1025 jn amsterdam, nederland; e-mail: dik@cwi.nl