Strachey Method For Magic Squares

The Strachey method for magic squares is an algorithm for generating magic squares of singly even order 4n+2.

Example of magic square of order 6 constructed with the Strachey method:

Example
35 1 6 26 19 24
3 32 7 21 23 25
31 9 2 22 27 20
8 28 33 17 10 15
30 5 34 12 14 16
4 36 29 13 18 11

Strachey's method of construction of singly even magic square of order k=4*n+2

1. Divide the grid into 4 quarters each having k^2/4 cells and name them crosswise thus

A C
D B

2. Using the Siamese method (De la Loubère method) complete the individual magic squares of odd order 2*n+1 in subsquares A, B, C, D, first filling up the sub-square A with the numbers 1 to k^2/4, then the sub-square B with the numbers k^2/4 +1 to 2*k^2/4,then the sub-square C with the numbers 2*k^2/4 +1 to 3*k^2/4, then the sub-square D with the numbers 3*k^2/4 +1 to k^2.

17 24 1 8 15 67 74 51 58 65
23 5 7 14 16 73 55 57 64 66
4 6 13 20 22 54 56 63 70 72
10 12 19 21 3 60 62 69 71 53
11 18 25 2 9 61 68 75 52 59
92 99 76 83 90 42 49 26 33 40
98 80 82 89 91 48 30 32 39 41
79 81 88 95 97 29 31 38 45 47
85 87 94 96 78 35 37 44 46 28
86 93 100 77 84 36 43 50 27 34

3. Exchange the leftmost n columns in sub-square A with the corresponding columns of sub-square D.

92 99 1 8 15 67 74 51 58 65
98 80 7 14 16 73 55 57 64 66
79 81 13 20 22 54 56 63 70 72
85 87 19 21 3 60 62 69 71 53
86 93 25 2 9 61 68 75 52 59
17 24 76 83 90 42 49 26 33 40
23 5 82 89 91 48 30 32 39 41
4 6 88 95 97 29 31 38 45 47
10 12 94 96 78 35 37 44 46 28
11 18 100 77 84 36 43 50 27 34

4. Exchange the rightmost n-1 columns in sub-square C with the corresponding columns of sub-square B.

92 99 1 8 15 67 74 51 58 40
98 80 7 14 16 73 55 57 64 41
79 81 13 20 22 54 56 63 70 47
85 87 19 21 3 60 62 69 71 28
86 93 25 2 9 61 68 75 52 34
17 24 76 83 90 42 49 26 33 65
23 5 82 89 91 48 30 32 39 66
4 6 88 95 97 29 31 38 45 72
10 12 94 96 78 35 37 44 46 53
11 18 100 77 84 36 43 50 27 59

5. Exchange the middle cell of the leftmost column of sub-square A with the corresponding cell of sub-square D. Exchange the central cell in sub-square A with the corresponding cell of sub-square D.

92 99 1 8 15 67 74 51 58 40
98 80 7 14 16 73 55 57 64 41
4 81 88 20 22 54 56 63 70 47
85 87 19 21 3 60 62 69 71 28
86 93 25 2 9 61 68 75 52 34
17 24 76 83 90 42 49 26 33 65
23 5 82 89 91 48 30 32 39 66
79 6 13 95 97 29 31 38 45 72
10 12 94 96 78 35 37 44 46 53
11 18 100 77 84 36 43 50 27 59

The result is a magic square of order k=4*n+2.

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