Pandiagonal magic square

From HandWiki

A pandiagonal magic square or panmagic square (also diabolic square, diabolical square or diabolical magic square) is a magic square with the additional property that the broken diagonals, i.e. the diagonals that wrap round at the edges of the square, also add up to the magic constant. A pandiagonal magic square remains pandiagonally magic not only under rotation or reflection, but also if a row or column is moved from one side of the square to the opposite side. As such, an n×n pandiagonal magic square can be regarded as having 8n2 orientations.

3×3 pandiagonal magic squares

It can be shown that non-trivial pandiagonal magic squares of order 3 do not exist. Suppose the square

a11a12a13a21a22a23a31a32a33

is pandiagonally magic with magic constant s. Adding sums a11+a22+a33, a12+a22+a32, and a13+a22+a31 results in 3s. Subtracting a11+a12+a13 and a31+a32+a33, we get 3a22=s. However, if we move the third column in front and perform the same argument, we obtain 3a22=s. In fact, using the symmetries of 3 × 3 magic squares, all cells must equal 13s. Therefore, all 3 × 3 pandiagonal magic squares must be trivial.

However, if the magic square concept is generalized to include geometric shapes instead of numbers – the geometric magic squares discovered by Lee Sallows – a 3 × 3 pandiagonal magic square does exist.

4×4 pandiagonal magic squares

Euler diagram of requirements of some types of 4 × 4 magic squares. Cells of the same colour sum to the magic constant.

The smallest non-trivial pandiagonal magic squares are 4 × 4 squares. All 4 × 4 pandiagonal magic squares must be translationally symmetric to the form[1]

a a + b + c + e a + c + d a + b + d + e
a + b + c + d a + d + e a + b a + c + e
a + b + e a + c a + b + c + d + e a + d
a + c + d + e a + b + d a + e a + b + c

Since each 2 × 2 subsquare sums to the magic constant, 4 × 4 pandiagonal magic squares are most-perfect magic squares. In addition, the two numbers at the opposite corners of any 3 × 3 square add up to half the magic constant. Consequently, all 4 × 4 pandiagonal magic squares that are associative must have duplicate cells.

All 4 × 4 pandiagonal magic squares using numbers 1-16 without duplicates are obtained by letting a equal 1; letting b, c, d, and e equal 1, 2, 4, and 8 in some order; and applying some translation. For example, with b = 1, c = 2, d = 4, and e = 8, we have the magic square

1 12 7 14
8 13 2 11
10 3 16 5
15 6 9 4

The number of 4 × 4 pandiagonal magic squares using numbers 1-16 without duplicates is 384 (16 times 24, where 16 accounts for the translation and 24 accounts for the 4! ways to assign 1, 2, 4, and 8 to b, c, d, and e).

5×5 pandiagonal magic squares

There are many 5 × 5 pandiagonal magic squares. Unlike 4 × 4 pandiagonal magic squares, these can be associative. The following is a 5 × 5 associative pandiagonal magic square:

20 8 21 14 2
11 4 17 10 23
7 25 13 1 19
3 16 9 22 15
24 12 5 18 6

In addition to the rows, columns, and diagonals, a 5 × 5 pandiagonal magic square also shows its magic constant in four "quincunx" patterns, which in the above example are:

17+25+13+1+9 = 65 (center plus adjacent row and column squares)
21+7+13+19+5 = 65 (center plus the remaining row and column squares)
4+10+13+16+22 = 65 (center plus diagonally adjacent squares)
20+2+13+24+6 = 65 (center plus the remaining squares on its diagonals)

Each of these quincunxes can be translated to other positions in the square by cyclic permutation of the rows and columns (wrapping around), which in a pandiagonal magic square does not affect the equality of the magic constants. This leads to 100 quincunx sums, including broken quincunxes analogous to broken diagonals.

The quincunx sums can be proved by taking linear combinations of the row, column, and diagonal sums. Consider the pandiagonal magic square

a11a12a13a14a15a21a22a23a24a25a31a32a33a34a35a41a42a43a44a45a51a52a53a54a55

with magic constant s. To prove the quincunx sum a11+a15+a33+a51+a55=s (corresponding to the 20+2+13+24+6 = 65 example given above), we can add together the following:

3 times each of the diagonal sums a11+a22+a33+a44+a55 and a15+a24+a33+a42+a51,
The diagonal sums a11+a25+a34+a43+a52, a12+a23+a34+a45+a51, a14+a23+a32+a41+a55, and a15+a21+a32+a43+a54,
The row sums a11+a12+a13+a14+a15 and a51+a52+a53+a54+a55.

From this sum, subtract the following:

The row sums a21+a22+a23+a24+a25 and a41+a42+a43+a44+a45,
The column sum a13+a23+a33+a43+a53,
Twice each of the column sums a12+a22+a32+a42+a52 and a14+a24+a34+a44+a54.

The net result is 5a11+5a15+5a33+5a51+5a55=5s, which divided by 5 gives the quincunx sum. Similar linear combinations can be constructed for the other quincunx patterns a23+a32+a33+a34+a43, a13+a31+a33+a35+a53, and a22+a24+a33+a42+a44.

(4n+2)×(4n+2) pandiagonal magic squares with nonconsecutive elements

No pandiagonal magic square exists of order 4n+2 if consecutive integers are used. But certain sequences of nonconsecutive integers do admit order-(4n+2) pandiagonal magic squares.

Consider the sum 1+2+3+5+6+7 = 24. This sum can be divided in half by taking the appropriate groups of three addends, or in thirds using groups of two addends:

1+5+6 = 2+3+7 = 12
1+7 = 2+6 = 3+5 = 8

An additional equal partitioning of the sum of squares guarantees the semi-bimagic property noted below:

12 + 52 + 62 = 22 + 32 + 72 = 62

Note that the consecutive integer sum 1+2+3+4+5+6 = 21, an odd sum, lacks the half-partitioning.

With both equal partitions available, the numbers 1, 2, 3, 5, 6, 7 can be arranged into 6 × 6 pandigonal patterns A and B, respectively given by:

1 5 6 7 3 2
5 6 1 3 2 7
6 1 5 2 7 3
1 5 6 7 3 2
5 6 1 3 2 7
6 1 5 2 7 3
6 5 1 6 5 1
1 6 5 1 6 5
5 1 6 5 1 6
2 3 7 2 3 7
7 2 3 7 2 3
3 7 2 3 7 2

Then 7A+B7C (where C is the magic square with 1 for all cells) gives the nonconsecutive pandiagonal 6 × 6 square:

6 33 36 48 19 8
29 41 5 15 13 47
40 1 34 12 43 20
2 31 42 44 17 14
35 37 3 21 9 45
38 7 30 10 49 16

with a maximum element of 49 and a pandiagonal magic constant of 150. This square is pandiagonal and semi-bimagic, that means that rows, columns, main diagonals and broken diagonals have a sum of 150 and, if we square all the numbers in the square, only the rows and the columns are magic and have a sum of 5150.

For 10th order a similar construction is possible using the equal partitionings of the sum 1+2+3+4+5+9+10+11+12+13 = 70:

1+3+9+10+12 = 2+4+5+11+13 = 35
1+13 = 2+12 = 3+11 = 4+10 = 5+9 = 14
12 + 32 + 92 + 102 + 122 = 22 + 42 + 52 + 112 + 132 = 335 (equal partitioning of squares; semi-bimagic property)

This leads to squares having a maximum element of 169 and a pandiagonal magic constant of 850, which are also semi-bimagic with each row or column sum of squares equal to 102,850.

(6n±1)×(6n±1) pandiagonal magic squares

A (6n±1)×(6n±1) pandiagonal magic square can be built by the following algorithm.

  1. Set up the first column of the square with the first 6n±1 natural numbers.
      1                                     
      2             
      3             
      4             
      5             
      6             
      7             
  2. Copy the first column into the second column but shift it ring-wise by 2 rows.
      1    6                               
      2    7           
      3    1           
      4    2           
      5    3           
      6    4           
      7    5           
  3. Continue copying the current column into the next column with ring-wise shift by 2 rows until the square is filled completely.
      1    6    4    2    7    5    3 
      2    7    5    3    1    6    4 
      3    1    6    4    2    7    5 
      4    2    7    5    3    1    6 
      5    3    1    6    4    2    7 
      6    4    2    7    5    3    1 
      7    5    3    1    6    4    2 
  4. Build a second square and copy the transpose of the first square into it.
    A
      1    6    4    2    7    5    3 
      2    7    5    3    1    6    4 
      3    1    6    4    2    7    5 
      4    2    7    5    3    1    6 
      5    3    1    6    4    2    7 
      6    4    2    7    5    3    1 
      7    5    3    1    6    4    2 
    AT
      1    2    3    4    5    6    7 
      6    7    1    2    3    4    5 
      4    5    6    7    1    2    3 
      2    3    4    5    6    7    1 
      7    1    2    3    4    5    6 
      5    6    7    1    2    3    4 
      3    4    5    6    7    1    2 
  5. Build the final square by multiplying the second square by 6n±1, adding the first square and subtract 6n±1 in each cell of the square.

    Example: A+(6n±1)AT(6n±1)B, where B is the magic square with all cells as 1.

      1   13   18   23   35   40   45 
     37   49    5   10   15   27   32 
     24   29   41   46    2   14   19 
     11   16   28   33   38   43    6 
     47    3    8   20   25   30   42 
     34   39   44    7   12   17   22 
     21   26   31   36   48    4    9 

4n×4n pandiagonal magic squares

A 4n×4n pandiagonal magic square can be built by the following algorithm.

  1. Put the first 2n natural numbers into the first row and the first 2n columns of the square.
      1    2    3    4                         
                   
                   
                   
                   
                   
                   
                   
  2. Put the next 2n natural numbers beneath the first 2n natural numbers in reverse. Each vertical pair must have the same sum.
      1    2    3    4                         
      8    7    6    5                         
                   
                   
                   
                   
                   
                   
  3. Copy that 2×2n rectangle 2n1 times beneath the first rectangle.
      1    2    3    4                         
      8    7    6    5                         
      1    2    3    4                         
      8    7    6    5                         
      1    2    3    4                         
      8    7    6    5                         
      1    2    3    4                         
      8    7    6    5                         
  4. Copy the left 4n×2n rectangle into the right 4n×2n rectangle but shift it ring-wise by one row.
      1    2    3    4    8    7    6    5 
      8    7    6    5    1    2    3    4 
      1    2    3    4    8    7    6    5 
      8    7    6    5    1    2    3    4 
      1    2    3    4    8    7    6    5 
      8    7    6    5    1    2    3    4 
      1    2    3    4    8    7    6    5 
      8    7    6    5    1    2    3    4 
  5. Build a second 4n×4n square and copy the first square into it but turn it by 90°.
    A
      1    2    3    4    8    7    6    5 
      8    7    6    5    1    2    3    4 
      1    2    3    4    8    7    6    5 
      8    7    6    5    1    2    3    4 
      1    2    3    4    8    7    6    5 
      8    7    6    5    1    2    3    4 
      1    2    3    4    8    7    6    5 
      8    7    6    5    1    2    3    4 
    B
      5    4    5    4    5    4    5    4 
      6    3    6    3    6    3    6    3 
      7    2    7    2    7    2    7    2 
      8    1    8    1    8    1    8    1 
      4    5    4    5    4    5    4    5 
      3    6    3    6    3    6    3    6 
      2    7    2    7    2    7    2    7 
      1    8    1    8    1    8    1    8 
  6. Build the final square by multiplying the second square by 4n, adding the first square and subtract 4n in each cell of the square.

    Example: A+4nB4nC, where C is the magic square with all cells as 1.

     33   26   35   28   40   31   38   29 
     48   23   46   21   41   18   43   20 
     49   10   51   12   56   15   54   13 
     64    7   62    5   57    2   59    4 
     25   34   27   36   32   39   30   37 
     24   47   22   45   17   42   19   44 
      9   50   11   52   16   55   14   53 
      8   63    6   61    1   58    3   60 

If we build a 4n×4n pandiagonal magic square with this algorithm then every 2×2 square in the 4n×4n square will have the same sum. Therefore, many symmetric patterns of 4n cells have the same sum as any row and any column of the 4n×4n square. Especially each 2n×2 and each 2×2n rectangle will have the same sum as any row and any column of the 4n×4n square. The 4n×4n square is also a most-perfect magic square.

(6n+3)×(6n+3) pandiagonal magic squares

A (6n+3)×(6n+3) pandiagonal magic square can be built by the following algorithm.

  1. Create a (2n+1)×3 rectangle with the first 6n+3 natural numbers so that each column has the same sum. You can do this by starting with a 3 × 3 magic square and set up the rest cells of the rectangle in meander-style. You can also use the pattern shown in the following examples.
    For 9 × 9 square
     1   2   3 
     5   6   4 
     9   7   8 
    vertical sum = 15
    For 15 × 15 square
     1   2   3 
     5   6   4 
     9   7   8 
     10   11   12 
     15   14   13 
    vertical sum = 40
    For 21 × 21 square
     1   2   3 
     5   6   4 
     9   7   8 
    10 11 12
    15 14 13
    16 17 18
    21 20 19
    vertical sum = 77
  2. Put this rectangle in the left upper corner of the (6n+3)×(6n+3) square and two copies of the rectangle beneath it so that the first 3 columns of the square are filled completely.
      1    2    3 
      5    6    4 
      9    7    8 
      1    2    3 
      5    6    4 
      9    7    8 
      1    2    3 
      5    6    4 
      9    7    8                                     
  3. Copy the left 3 columns into the next 3 columns, but shift it ring-wise by 1 row.
      1    2    3    9    7    8 
      5    6    4    1    2    3 
      9    7    8    5    6    4 
      1    2    3    9    7    8 
      5    6    4    1    2    3 
      9    7    8    5    6    4 
      1    2    3    9    7    8 
      5    6    4    1    2    3 
      9    7    8    5    6    4                   
  4. Continue copying the current 3 columns into the next 3 columns, shifted ring-wise by 1 row, until the square is filled completely.
      1    2    3    9    7    8    5    6    4 
      5    6    4    1    2    3    9    7    8 
      9    7    8    5    6    4    1    2    3 
      1    2    3    9    7    8    5    6    4 
      5    6    4    1    2    3    9    7    8 
      9    7    8    5    6    4    1    2    3 
      1    2    3    9    7    8    5    6    4 
      5    6    4    1    2    3    9    7    8 
      9    7    8    5    6    4    1    2    3 
  5. Build a second square and copy the transpose of the first square into it.
    A
      1    2    3    9    7    8    5    6    4 
     5   6   4   1   2   3   9   7   8 
     9   7   8   5   6   4   1   2   3 
     1   2   3   9   7   8   5   6   4 
     5   6   4   1   2   3   9   7   8 
     9   7   8   5   6   4   1   2   3 
     1   2   3   9   7   8   5   6   4 
     5   6   4   1   2   3   9   7   8 
     9   7   8   5   6   4   1   2   3 
    AT
      1    5    9    1    5    9    1    5    9 
     2   6   7   2   6   7   2   6   7 
     3   4   8   3   4   8   3   4   8 
     9   1   5   9   1   5   9   1   5 
     7   2   6   7   2   6   7   2   6 
     8   3   4   8   3   4   8   3   4 
     5   9   1   5   9   1   5   9   1 
     6   7   2   6   7   2   6   7   2 
     4   8   3   4   8   3   4   8   3 
  6. Build the final square by multiplying the second square by 6n+3, adding the first square and subtract 6n+3 in each cell of the square.

    Example: A+(6n+3)AT(6n+3)B, where B is the magic square with all cells as 1.

     1   38   75   9   43   80   5   42   76 
     14   51   58   10   47   57   18   52   62 
     27   34   71   23   33   67   19   29   66 
     73   2   39   81   7   44   77   6   40 
     59   15   49   55   11   48   63   16   53 
     72   25   35   68   24   31   64   20   30 
     37   74   3   45   79   8   41   78   4 
     50   60   13   46   56   12   54   61   17 
     36   70   26   32   69   22   28   65   21 

References

  • W. S. Andrews, Magic Squares and Cubes. New York: Dover, 1960. Originally printed in 1917. See especially Chapter X.
  • Ollerenshaw, K., Brée, D.: Most-perfect pandiagonal magic squares. IMA, Southend-on-Sea (1998)