# Magic 3-D Polygons & Graphs

On this page we will digress a little and consider 3 and 4 dimensional objects and other types of graphs.
Actually, many of these are not polygons, but can have similar magical properties to perimeter magic polygons.
I have taken many of thee drawings from
[1], and present them with a minimum of descriptive text.

[1] H. D. Heinz and J. R. Hendricks, Magic Square Lexicon: Illustrated, 2000, , 184pp +

 Face magic and anti-magic cubes Edge Magic Tetrahedrons M-type Edge Magic Tetrahedrons Perimeter Face Anti-magic Octahedrons Mapping and Perimeter Magic Face Magic Stacked Parallelograms Magic Dodecahedron Tree-planting Graphs Super and Anti-magic Graphs Different Magic Triangles Magic Circles More Magic Graphs Graceful Graphs Some problems References

Face magic and anti-magic cubes

Magic
The first eight digits can be placed on the corners (vertices) of a cube in 1680 different ways. It is possible to place them in such a manner that the sum of the four integers on each of the six faces sum to the same value.
It turns out that the there is only one set of two groups of four that can be used to construct an order-2 face magic cube. That is 1, 4, 6, 7 and 2, 3, 5, 8. These two sets can be placed on opposite faces of the cube to produce 6 different order-2, face magic solutions. All have face sums of 18.
[2]
Figure A. is one of the six solutions.

Anti-magic
It is possible to place the digits 1 to 8 on the vertices of a cube in such a manner that each face sums to a different value. If these sums are in arithmetic progression, the cube is anti-magic.
Figures B and C are two of the 13 possible solutions. 12 of these consist of 6 complement pairs, one is self-complementing.

There are no edge-magic or anti-magic order-2 cubes. However, the sums of 11 of the 12 edges of Figure D are prime numbers (but with duplication). [3]

Can you find solutions to order-3 face or edge magic cubes?

[2] C. W. Trigg, Second Order Perimeter-magic and Perimeter-antimagic Cubes, Mathematics Magazine, 47(3), 1974, pp.95-97.
[3] C. W. Trigg, Eight Digits on a Cubes Vertices, Journal of Recreational Mathematics, 7:1, 1974, pp.49-55, .

Edge Magic Tetrahedrons

Magic
There are no order-2 (Trigg calls these V-type) edge magic tetrahedrons. [3]

There are no order-3 edge magic tetrahedrons (using consecutive integers)
Figures A, B, and C illustrate three non-normal solutions. A does not use the integer 4, B. does not use the integers 1 or 11, C. Does not use the integer 2.

Anti-magic
There are no order-2 edge anti-magic tetrahedrons.
There are a total of 376 edge anti-magic tetrahedrons of order 3 (Trigg calls these VM-type) with edge sums in arithmetic progression. Figure D. is one solution .
Figure E is a richer solution (1 of 16 of this type). The edge sums are 7, 8, 9, 10, 11, 12, and the vertex only sums (i.e. order-2) are 3, 4, 5, 6; giving ten consecutive sums!

Magic
If one digit is placed at each edge midpoint (none at the vertices), the polygon is trivially edge anti-magic.
The first12 integers may be placed in pairs near the midpoints of the edges (of the tetrahedron), so that all edges sum the same. Figure A

Anti-magic
There are a large number of edge anti-magic tetrahedrons of this type. B and C show two of them.

[4] C. W. Trigg, Edge-Magic and Edge-Antimagic Tetrahedrons, Journal of Recreational Mathematics, 4:4, 1971, pp.253-259, .

As all the faces of a polyhedron are triangles, it is impossible to place distinct integers on its vertices so that every triangle will have the same perimeter sum. Therefore, no such polyhedron can be magic. However, if the perimeter sums are all different the polyhedron will be perimeter anti-magic.

In the case of an octahedron it turns out that there are 15 basic ways to distribute the digits 1 to 6 on the vertices with eight different perimeter sums. Of these 15, five produce distinct perimeter sums for the eight triangles and so are perimeter anti-magic.

Figures A. and B. may each be complemented by subtracting each number from 7, to provide another solution. C. is self-complementing.

D. shows the basic way to arrange the integers 1 to 4 on the vertices of a tetrahedron. The perimeter sums are in the arithmetic progression order 6, 7, 8, 9, making this a true, face anti-magic tetrahedron. The edge sums of D are almost unique, meaning this is also an almost edge anti-magic tetrahedron!

These figures are order-2 (2 integers per edge). Investigations into order-3 (and higher) figures of this type are still required.

[5] C. W. Trigg, Perimeter Anti-magic tetrahedrons and Octahedrons, Journal of Recreational Mathematics, 11:2, 1978-79, pp.105-107.

Mapping and Perimeter Magic

Mapping is a transformation of one image into another one.

In A., the cube is face perimeter magic with the vertices mapping to the triangles of the star. The octahedron is vertex magic with the edges of the eight triangles mapping to the star triangles.

In B. the order-4 magic square is mapped to an order 2 perimeter magic tetrahedron.

Face Magic Stacked Parallelograms

 The corner numbers of these 16 parallelograms all sum to 34 (i.e. face magic), as do the 4 numbers in each of the four vertical lines. They were mapped from the order 4 pantriagonal magic square shown. More on Perimeter magic cubes is on my Unusual magic cubes page. [6] [6] See my previously written article on perimeter magic cubes (on my unusual cubes page).

Magic Dodecahedron

 Shown here is a Schlegel diagram (graph) of the platonic solid 12 faced dodecahedron. The numbers 1 to 25 are placed at the vertices of the faces in such a way that all 12 faces are magic. The diagram is placed inside a circle and 5 radial lines have been added. These lines and the circle also sum to the constant. This diagram was taken from a book published in Russia in 1964. [7] [7] A. P. Domoryad, Mathematical Games and Pastimes, Russia, 1964, page 103.

Tree-planting Graphs

 Your aid I want, nine trees to plant    In rows just half a score; And let there be in each row three.     Solve this: I ask no more. In 1821, John Jackson published this ditty in Rational Amusements for Winter Evenings. Figure A. is the answer to Jackson’s little poem.

Tree-planting graphs are so-called because they result from the effort to arrange as many “trees” as possible in a minimum number of lines, each containing the same number of “trees”. This problem was made popular by H. E, Dudeney (but introduced by John Jackson 75 years earlier).
See [8] for a good introduction to this type of problem, although you will find it mentioned in many books on recreational mathematics.

In keeping to the theme of magic perimeters and graphs, I like to replace the ‘trees” with consecutive integers in such a way that the lines are magic. Figure B. is the order 3 magic square with 8 lines of 3 numbers all adding to the same constant.

The figure below illustrates an order-5 magic star I have mapped to  5 other isomorphic “tree-planting” graphs. [1]
These 6 graphs all have 10 numbers that appear in 5 lines of 4 numbers. Notice however, that unlike most examples I have shown, these 10 numbers are not consecutive. It is impossible to place the numbers 1 to 10 on a 5-pointed star so that all lines sum the same.

[1] H. D. Heinz and J. R. Hendricks, Magic Square Lexicon: Illustrated, 2000, , 184pp +
[8] Mathematical Recreations, Edited by David A. Klarner, Dover Publ., 1998, 0-486-40089-1, Planting Trees, by Stefan Burr, pp90-99.

Graph – super-magic

A graph with q edges is said to be super-magic if it is possible to label the edges with the numbers 1, 2, 3, …, q in such a way that at each vertex v the sum of the labels on the edges incident with v is the same.

Many super-magic graphs are isomorphic to magic squares, as the following examples illustrate. Solid vertices in these graphs represent the rows of the magic square., hollow vertices the columns. These graphs is bipartite because no two like vertices are directly connected by an edge.

Graph - Anti-magic

A graph with q edges is said to be anti-magic if it is possible to label the edges with the numbers 1, 2, 3, …, q in such a way that at each vertex v the sum of the labels on the edges incident with v is different.

Many anti-magic graphs are isomorphic to magic squares, as the following example illustrates. This graph is isomorphic to the order-4 anti-magic square shown in Anti-magic squares. Solid vertices in this graph represent the rows of the magic square., hollow vertices the columns.

Note that unlike anti-magic squares, it is not required that anti-magic graphs have the sums form a consecutive series. In fact, for normal anti-magic squares, at least 1 of the two diagonals must sum to a value in the middle of the series. In the case of this graph, the sums form a series from 30 to 38 but with 34 missing.

[9] Hartsfield & Ringel, Supermagic and Antimagic Graphs, Journal of Recreational Mathematics, 21:2, 1989, pp107-115

Different Magic Triangles

 Absolute Difference triangle In this triangle, the number at the apex is the difference between the two numbers on the base of the triangle. This is the only order-5 absolute difference triangle using the consecutive integers from 1 to 15. There are two order-2, four order-3, and four order-4 such triangles. It is thought that there are no absolute difference triangles higher then order-5 using consecutive integers. [10] [10] C. W. Trigg, Absolute Difference Triangles, Journal of Recreational Mathematics, 9:4, 1977, pp.271-275.

 Fractal Triangles Figure A. shows nested triangles with a single digit at the apex of each triangle. If you consider the digit at each end of a line  (ie. adjacent vertices) forming two 2 digit numbers, one of these two numbers will always be divisible by seven (in these examples). This example is called a cycle 1 because it oscillates between identical triangles. Figure B. is an example of a cycle 4 Fractal Triangle because, starting from the center there are four different triangles before the center triangle repeats as the outer triangle. The author conjectures that no longer cycles are possible. [11] C. Pickover, C. Ashbacher, Problem 2025, Fractal Triangles, Journal of Recreational Mathematics, 26:1, 1994, pp.69-70.

Magic Circles

Another magic object related to magic squares, graphs, etc. is the magic circle. Benjamin Franklin, when talking about his famous magic squares, mentioned a magic circle derived from one. See a recreation of this on my Franklin Magic Squares page. [12]

Here I show a set of magic circles, all related to the same order-4 pandiagonal magic square. It is number 469 in the sorted list of all 880 order-4 basic magic squares. All 48 pandiagonal magic squares of this order contain all the patterns shown in this set of four graphs. This is not necessarily true for other orders of pandiagonal magic squares.

1. A., in the figure, is the magic square I use for this example. Shown are the basic requirements for all magic squares (ie all rows, columns, and the two main diagonals must sum to a constant. To be classed as pandiagonal, two other patterns are required. These appear in parts C. and D.

2. B. Contains 9 small circles, each of which connect to 4 numbers that sum to the constant 34. Also, shown in B. are 4 medium sized circles and one large circle, all of which also connect to 4 numbers summing to 34.

3. C. contains 2 diagonal ovals which show a pattern required to make the square pandiagonal. C. also shows 3 vertical and 3 horizontal ovals illustrating another magic pattern

4. D. shows 8 sets of four numbers connected by distorted ovals. All of these sets also sum to 34. Also shown are 4 sets of four numbers connected by triangles. This is the other pattern that is a requirement of pandiagonal magic squares.

 This set of 4 graphs illustrate a total of 9 patterns (2+3+2+2) that appear in an order-4 pandiagonal magic square. All combinations of 4 numbers sum to the constant 34.     However, there is one additional pattern in the magic square that is not shown in diagrams B, C or D. Can you find it?     See a pandiagonal magic square generator using a magic torus on my Unusual Squares page. [12] An elaborate magic circle appears on my Franklin page. And a Prime circle on my More primes page.

 The six numbers on each of the four circles sum to 39. Each spoke (including the hub) and each rim section sum to 38. The middle number on each line is the difference between the two outside numbers.

More Magic Graphs

Graphs A and B are self-explanatory. In the “3-D” graph at C, the sum of the 5 lines at each node is 65.

A and B are from [9], C is from [1] and [9]

 10 nodes The 10 nodes in this graph are each connected to all the others with lines (edges) labelled with the consecutive numbers from 1 to 45. The 9 lines connected to each node sum to the same constant 207. Dominic Olivastro explains how to construct this type of graph in [16], pages 121-125 (using a 6 node graph as an example).  Priming the cube The corners of this cube are labeled with the consecutive integers from 0 to 7 in such a way that two adjacent corners (vertices) always sum to a prime number.

[13] See another prime number graph containing numbers 1 to 22 on my Prime Numbers page.
"Magic Hexagons" and "12 Magic Circles-6 Magic Squares" are on my More Squares page.

Graceful Graphs

 In 1972, Solomon Golomb proposed a new type of graph numbering called Graceful Graphs. [14] In it, the nodes are numbered in such a way that the edges connecting them form a set of consecutive numbers starting with 1. The lowest node number is zero, and by necessity, the node numbers are not consecutive. For a graft to be graceful, the highest node number, the highest edge number, and the number of edges must all be equal. Figure A (below) is a tetrahedron and figure C is a Schlegel representation of a cube. Notice in figure B, one line seems to be missing. If that line is added, the diagram becomes one of only 3 ungraceful graphs with fewer then 6 nodes! These graceful graphs are all from Martin Gardner's  Mathematical Games column in Scientific American Magazine . [14] [15]

[14] Martin Gardner, Mathematical Games, Scientific American Magazine, March,1972, pp 108-112.
[15] Martin Gardner, Wheels, Life, and Other Mathematical Amusements, W. H. Freeman, 1983, 0-7167-1589-9, pp 152-165, Golomb’s Graceful Graphs

Some problems

Tree Problems
These are my patterns. Can you assign consecutive numbers to them so that each line equals the same value?
several more tree planting problems appear on my Magic Star Updates page.

Graceful graph problems
These three graphs are taken from Gardner's column [14] [15] and presented here as problems. His column provides the solutions.
Figure A will use edge numbers 1 to 9 and B will use 1 to 22. C will use numbers 1 to 25 for the edges and 0 to 25 for the nodes.

References

[1] H. D. Heinz and J. R. Hendricks, Magic Square Lexicon: Illustrated, 2000, , 184pp +
[2] C. W. Trigg, Second Order Perimeter-magic and Perimeter-antimagic Cubes, Mathematics Magazine, 47(3), 1974, pp.95-97.
[3] C. W. Trigg, Eight Digits on a Cubes Vertices, Journal of Recreational Mathematics, 7:1, 1974, pp.49-55,.
[4] C. W. Trigg, Edge-Magic and Edge-Antimagic Tetrahedrons, Journal of Recreational Mathematics, 4:4, 1971, pp.253-259, .
[5] C. W. Trigg, Perimeter Anti-magic tetrahedrons and Octahedrons, Journal of Recreational Mathematics, 11:2, 1978-79, pp.105-107.
[6] See my previously written article on perimeter magic cubes (on my unusual cubes page).
[7] A. P. Domoryad, Mathematical Games and Pastimes, Russia, 1964, page 103.
[8] Mathematical Recreations, Edited by David A. Klarner, Dover Publ., 1998, 0-486-40089-1, Planting Trees, by Stefan Burr, pp90-99.
[9] Hartsfield & Ringel, Supermagic and Antimagic Graphs, Journal of Recreational Mathematics, 21:2, 1989, pp107-115
[10] C. W. Trigg, Absolute Difference Triangles, Journal of Recreational Mathematics, 9:4, 1977, pp.271-275.
[11] C. Pickover, C. Ashbacher, Problem 2025, Fractal Triangles, Journal of Recreational Mathematics, 26:1, 1994, pp.69-70.
[12] An elaborate magic circle appears on my Franklin page. And a Prime circle on my More primes page.
[13] See another prime number graph containing numbers 1 to 22 on my Prime Numbers page.
And "Magic Hexagons" and "12 Magic Circles-6 Magic Squares" are on my More Squares page.
[14] Martin Gardner, Mathematical Games, Scientific American Magazine, March,1972, pp 108-112.
[15] Martin Gardner, Wheels, Life, and Other Mathematical Amusements, W. H. Freeman, 1983, 0-7167-1589-9, pp 152-165, Golomb’s Graceful Graphs

 This page was originally posted October 2006 It was last updated October 12, 2010 Harvey Heinz   harveyheinz@shaw.ca Copyright © 1998-2009 by Harvey D. Heinz