How many a 3x3 magic squares using only the 1st nine non-composite numbers exist?
(In reply to Solution
The number 1 is not composite (it's not prime either, but that's not relevant), so the numbers in question are 1, 2, 3, 5, 7, 11, 13, 17 and 19. These add up to 78, which is in fact divisible by 3, so the reasoning given does not apply.
Posted by Charlie
on 2017-11-08 15:49:59