Urgent Help Needed PLEASE

Hi i am trying to solve a number grid problem by 4x4 block finding the product of the top left number and the bottom right number in the block doing the same with the top right and bottom left numbers. Calculating the difference so far this is what i have done

1 2 3 4

11 12 13 14

21 22 23 24

31 32 33 34

I have chosen 1 as the upper left

Multiply 1 x 12 x 23 x 34 = 9384

Multiply 4 x 13 x 22 x 31 = 35464

Difference = 26080

Next 4x4 block

2 3 4 5

12 13 14 15

22 23 24 25

32 33 34 35

Multiply 2 x 13 x 24 x 35 =21840

Multiply 5 x 14 x 23 x 32 = 51520

Difference = 29680

Notice that there is a difference of 3600 between the 1st and the 2nd block (29680 - 2608 = 3600)

I then did another 4x4 block where 3 was the upper left and another 4x4 block 4 as the upper left and got a difference of 3800 i am so confused can any kind person pls explain am i doing this right and how can i generate a formula of D (DIFFERENCE) involving N (NUMBER OF SQUARES). your help would be very much appreciated also if you can explain the 5x5 block

Thank you:confused: :confused: :confused: :confused: