Problems & Puzzles: Puzzles

Puzzle 288.  Magic squares of (prime) squares

It's believed that is impossible to construct a 3x3 magic square of squares, but the proof has not been produced, not yet (*).

But, what about for higher orders?

Christian Boyer has sent the following 4x4 example, constructed by him, with the additional feature that the squares are prime-squares.

 292 1912 6732 1372 712 6472 1392 2572 2772 2112 1632 6012 6532 972 1012 2512

Magic sum=509020.

Boyer believes that this is the minimal magic sum for a 4x4 magic square of prime squares.

Questions:

1. Find the minimal 4x4 magic square of squares?

2. Find the minimal nxn magic square of prime squares, for n=5, 6, 7 & 8.

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(*) except by the probable hoax by Chebrakov. See our puzzle 79.

Contributions came from Christian Boyer and Giovanni Resta. J. C. Rosa has sent a contribution to the Puzzle 79, close related to this puzzle, so it would be a good idea to go there.

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Boyer has sent the minimal 4x4 magic square of squares. As a matter of fact this square was found by other person in 2001 and Boyer has verified that it certainly is the minimal one. But I will not publish it in order to encourage the readers of these pages to re-discover it.

Boyer has confirmed also that his prime magic square of squares shown above, is in fact the minimal one and has sent another one that he thinks is the second smallest.

23² 353² 761² 179²
641² 331² 263² 383²
409² 691² 283² 107²
397² 157² 89² 739²
Magic sum = 736300.

He has also sent the smallest solution to the case 5x5, for the question 2. Again I will not publish it yet until other puzzler send one more solution.

Boyer announces that he "will let to other people the pleasure to find examples for k>=6."

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This 'other people' seems to be - by the moment Giovanni Resta, who has confirmed the two 4x4 prime magic squares of squares already sent by Boyer are in fact the smallest and the second smallest (which means that GR sent the same second smallest than CB) and sent also the third smallest:

701 571 79 193
269 317 311 769
67 659 479 439
541 11 727 199
Magical sum = 860932

Giovanni says" I'm in the process to find the minimal 5 x 5, but I've not the result yet".

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Christian Boyer wrote (July 2005):

Good news. My article "Some notes on the magic squares of squares problem"
is now published in the new issue of The Mathematical Intelligencer.
I was happy to quote your name, pages 58 and 64, with a reference to your puzzles 79, 287 and 288. And the names of Luke Pebody and Jean-Claude Rosa are also quoted for their proofs of the impossible 4x4 bimagic square (puzzle 287).

I have created a new page "Magic squares of squares" in my web site www.multimagie.com/indexengl.htm  And there is an unpublished supplement to my article, available from this new page: because you will see that the square CB18 is the 5x5 solution of your puzzle 288, I think that you can now update your puzzle with this solution (I do not know if Giovanni has finished his "process to find the minimal 5 x 5"). See also this page by Boyer

 11² 23² 53² 139² 107² 13² 103² 149² 31² 17² 71² 137² 47² 67² 61² 113² 59² 41² 97² 83² 127² 29² 73² 7² 109²

CB18. The smallest 5×5 magic square of squares of prime numbers, S2 = 34229.

Latest news below: I have constructed 10 days ago the first known 6x6 and
7x7 magic squares of squares.
4x4 and 5x5 were already known (since 1770 and 2004 resp.). And the well-known bimagic squares of order 8 and + (since 1890) are magic squares of squares.
It means that the main remaining problem is the VERY difficult problem of
3x3 magic squares of squares!

Best regards.
Christian.

-------------------6x6
If I am right, 6x6 magic squares of squares using squared consecutive integers (0² to 35², or 1² to 36²) are impossible.
My 6x6 magic square of squares is NOT using squared consecutive integers...
but it is interesting to see the used numbers:
0² to 36² ONLY EXCLUDING 30².
It is impossible to construct a 6x6 magic square of squares with a smaller magic sum. But it is possible to construct other samples with the same magic sum S2 = 2551.

2² 1² 36² 5² 0² 35²
6² 33² 20² 29² 4² 13²
25² 7² 14² 24² 31² 12²
21² 32² 11² 15² 22² 16²
34² 18² 23² 10² 19² 9²
17² 8² 3² 28² 27² 26²

I have added a funny supplemental feature in this sample: the 3 smallest used integers (0, 1, 2) and the 2 biggest (35, 36) are used together in the first row.

-------------------7x7
If I am right, the smallest order allowing magic squares of squares using squared CONSECUTIVE integers seems to be the order 7.
An indirect consequence: the impossibility of 7x7 bimagic squares was not coming from a problem with squared numbers!
Here is a sample using integers 0² to 48², magic sum S2=5432.

25² 45² 15² 14² 44² 5² 20²
16² 10² 22² 6² 46² 26² 42²
48² 9² 18² 41² 27² 13² 12²
34² 37² 31² 33² 0² 29² 4²
19² 7² 35² 30² 1² 36² 40²
21² 32² 2² 39² 23² 43² 8²
17² 28² 47² 3² 11² 24² 38²

I have added a funny supplemental feature in this sample: the 7 rows are magic (S1=168) when the integers are not squared.

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