Construction methods
Here is the secret used to obtain tetra and pentamagic squares, the ViricelBoyer method for computing your own multimagic squares:

Col 0 
Col 1 
Col 2 
… 
Col i 
… 
Li 0 
0 = (0,0) 
N1 = (a,b) 
2@(a,b) 
… 
i@(a,b) 
… 
Li 1 
N2 = (c,d) 
(a,b) & (c,d) 
2@(a,b) & (c,d) 
… 
i@(a,b) & (c,d) 
… 
… 
… 
… 
… 
… 
… 
… 
Li j 
j@(c,d) 
(a,b) & j@(c,d) 
2@(a,b) & j@(c,d) 
… 
i@(a,b) & j@(c,d) 
… 
… 
… 
… 
… 
… 
… 
… 
The (a,b) notations indicates a number decomposed in base n (n being the square order).
Now take the example of our tetramagic square. See its top left corner:
0 
139938 
140551 
1957 
N1 = 139938 = 273*512(square order) + 162 So
(a,b) = (273,162)
N2 = 140551 = 274*512(square order) + 263 So (c,d) = (274,263)
We do not know the true rules which permit us to know if a pair N1 and N2 will generate a multimagic square. But you will find pairs, other than 139938/140551, which also give 512thorder tetramagic squares: the smallest are 535/1103, 535/1145, and so on...
What we call here the numeral addition « & » is well known by software developers : it is the EXCLUSIVE OR
& 
0 
1 
0 
0 
1 
1 
1 
0 
139938 = 100010001010100010
(in base 2)
140551 = 100010010100000111
(in base 2)
139938 & 140551
= 000000011110100101 (in base 2) = 1957 (in base 10).
And 1957 is really the number that we find in the tetramagic square seen above, under the 139938 number.
We will now compute the penultimate cell of the row 0 of our tetramagic square.
It is equal to 510@(273,162). We will start by computing 510@273:
510 = 111111110
(in base 2)
273 = 100010001
(in base 2)
The numeral multiplication is computed like the classical multiplication that we learn at school, except that the final addition is not done normally, but instead by numeral addition (so binary « exclusive or » ). It gives:
111111110
@ 100010001
111111110
& 111111110
& 111111110
= 011110000000011110
In order to conclude the multiplication and so that the number remains the same size as its two operands (lower than 512, so 9 bits coded), we carry out a supplemental numeral additon of the left and right parts of the result, like this:
011110000
& 000011110
= 011101110
So, the result of 510@273 is 11101110 in base 2, equal to 238 in our good old base 10. When, by the same method, we compute 510@162, we find 349.
So, the result of 510@(273,162) is (238,349) = 238*512 + 349 = 122205.
Have a look at the top right corner of our tetramagic square. We recognize this number in the penultimate cell of the row 0:
122205 
262143 
260186 
121592 
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