Magic cube class
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Every magic cube may be assigned to one of six magic cube classes, based on the cube characteristics.
Note that this is a relatively new definition. Until about 1995 there was much confusion about what constituted a perfect magic cube. Included below are references and links to discussions of the old definition
With the popularity of personal computers it became easier to examine the finer details of magic cubes. Also more and more work was being done with higher dimension magic Hypercubes. For example, John Hendricks constructed the worlds first perfect magic tesseract (perfect by this new definition) in 2000.
This new system is more precise in defining magic cubes. But possibly of more importance, it is consistent for all orders and all dimensions of magic hypercubes.
Minimum requirements for a cube to be magic are: All rows, columns, pillars, and 4 triagonals must sum to the same value.
Simple: The minimum requirements for a magic cube are: All rows, columns, pillars, and 4 triagonals must sum to the same value. A Simple magic cube contains no magic squares or not enough to qualify for the next class.
The smallest normal simple magic cube is order 3. See Simple magic cube.
Pantriagonal: All 4m2 pantriagonals must sum correctly (that is 4 one-segment, 12(m-1) two-segment, and 4(m-2)(m-1) three-segment). There may be some simple AND/OR pandiagonal magic squares, but not enough to satisfy any other classification.
The smallest normal pantriagonal magic cube is order 4. See Pantriagonal magic cube.
Diagonal: All 3m planar arrays must be simple magic squares. The 6 oblique squares are also simple magic. The smallest normal diagonal magic cube is order 5. These squares were referred to as ‘Perfect’ by Gardner and others! At the same time he referred to Langman’s 1962 pandiagonal cube also as ‘Perfect’. Christian Boyer and Walter Trump now consider this and the next two classes to be Perfect. A. H. Frost referred to these three classes as Nasik cubes.
The smallest normal diagonal magic cube is order 5. See Diagonal magic cube.
PantriagDiag: A cube of this class was first constructed in late 2004 by Mitsutoshi Nakamura. This cube is a combination Pantriagonal magic cube and Diagonal magic cube. Therefore, all main and broken triagonals sum correctly, and it contains 3m planar simple magic squares. In addition, all 6 oblique squares are pandiagonal magic squares. The only such cube constructed so far is order 8. It is not known what other orders are possible. See Pantriagdiag magic cube.
Pandiagonal: ALL 3m planar arrays must be pandiagonal magic squares. The 6 oblique squares are always magic (usually simple magic). Several of them MAY be pandiagonal magic. Gardner also called this (Langman’s pandiagonal) a ‘perfect’ cube, presumably not realizing it was a higher class then Myer’s cube. See previous note re Boyer and Trump.
The smallest normal pandiagonal magic cube is order 7. See Pandiagonal magic cube.
Perfect: ALL 3m planar arrays must be pandiagonal magic squares. In addition, ALL pantriagonals must sum correctly. These two conditions combine to provide a total of 9m pandiagonal magic squares.
The smallest normal perfect magic cube is order 8. See Perfect magic cube.
Generalized: A magic hypercube of dimension n is perfect if all pan-n-agonals sum correctly. Then all lower dimension hypercubes contained in it are also perfect!
Proper: A Proper magic cube is a magic cube belonging to one of the six classes of magic cube, but containing exactly the minimum requirements for that class of cube. i.e. a proper simple or pantriagonal magic cube would contain no magic squares, a proper diagonal magic cube would contain exactly 3m + 6 simple magic squares, etc. This term was coined by Mitsutoshi Nakamura in April, 2004.
A. H. Frost (1866) referred to all but the simple magic cube as Nasik!
Notes for table
- For the diagonal or pandiagonal classes, one or possibly 2 of the 6 oblique magic squares may be pandiagonal magic. All but 6 of the oblique squares are ‘broken’. This is analogous to the broken diagonals in a pandiagonal magic square. i.e. Broken diagonals are 1-D in a 2_D square; broken oblique squares are 2-D in a 3-D cube.
- The table shows the minimum lines or squares required for each class (i.e.Proper). Usually there are more, but not enough of one type to qualify for the next class.
[edit] References
Frost, Dr. A. H. On the General Properties of Nasik Cubes, QJM 15, 1878, pp 93-123
Heinz, H.D. and Hendricks, J. R., Magic Square Lexicon: Illustrated. Self-published, 2000, 0-9687985-0-0.
Hendricks, John R., The Pan-4-agonal Magic Tesseract, The American Mathematical Monthly, Vol. 75, No. 4, April 1968, p. 384.
Hendricks, John R., The Pan-3-agonal Magic Cube, Journal of Recreational Mathematics, 5:1, 1972, pp51-52
Hendricks, John R., The Pan-3-agonal Magic Cube of Order-5, JRM, 5:3, 1972, pp 205-206
Hendricks, John R., Magic Squares to Tesseracts by Computer, Self-published 1999. 0-9684700-0-9
Hendricks, John R., Perfect n-Dimensional Magic Hypercubes of Order 2n, Self-published 1999. 0-9684700-4-1
Pickover, Clifford A., The Zen of Magic Squares, Circles and Stars, Princeton Univ. Press, 2002, 0-691-07041-5 Pp 101, 121
http://cboyer.club.fr/multimagie/index.htm Christian Boyer: Perfect Magic Cubes
http://members.shaw.ca/hdhcubes/cube_perfect.htm Harvey Heinz: Perfect Magic Hypercubes
http://members.shaw.ca/hdhcubes/index.htm# Harvey Heinz:5 Classes of Cubes
http://www.trump.de/magic-squares/magic-cubes/cubes-1.html Walter Trump: Search for Smallest Perfect Cube
http://home.wanadoo.nl/aaledewinkel/Encyclopedia/ Aale de Winkel: Magic Encyclopedia
