First of all, the Rubik's Cube is equal to the sum of three diagonal lines. Let's assume for the time being that horizontal sum = vertical sum = oblique sum =a, so a+a+a= sum of all numbers =-4-3-2-1+1+2+3+4 = 0.

∴a=0 and -2 are in the middle, which means that any number must be on a line with -2 (this line can be horizontal, vertical or diagonal). At this point, it is observed that the grid must be filled with -4. Because a line must be found to make -4 and -2 on this line, there must be 6 that satisfies a=0.

Formula analysis:

Put 1 (or the smallest number) in the center of the first line; Arrange the remaining n*n- 1 numbers according to the following rules:

1, and each number is placed at the upper right of the previous number.

2. If the cell to put the number exceeds the top row, put it in the bottom row and still put it in the right column.

3. If the cell to put this number has exceeded the rightmost column, put it in the leftmost column and still put it in the previous row.