Originally Posted by Monique
View Post
For any amount m of sub-squares aimed for, one can choose m-1 sub-squares such that their sum is an odd number (i.e. by choosing an odd number of odd squares within them). This odd sum has to be the difference between two squares (as for any given odd number exist two squares differing by that number, as the difference between following squares is odd and increasing by 2 each time, n² = (n − 1)² + (2n − 1)). Therefore adding the lower of those 2 squares to our m-1 squares sums the m squares to yield the higher of the two squares.
Also, as Mon prodded forever more:
let the sum of the m-1 squares be of the form 2n-1 (as odd), and a and b be the 'final' pair of squares, so then we have
S+a²=b² or
S = (b-a)(b+a) now with b=a+1 and the above:
2n-1= b+a, therefore 2n-1=2a+1 or a=n-1, b= n
and to prove that a² is different for all previously chosen square numbers:
S= a² (+ possibly sum (of smaller squares)), with a² biggest square chosen,
therefore S≥a² and 2n-1≥a² and S/2 or n or n-1 all >a for all a≠ 1 or 2.
Comment