ok just listen to me, for linear sequences you have a gradient, a number that adds on to the current number every time what i call the incrementor goes up my one, ok so you have x * y, x is the incrementor, it just goes up and y is the gradient, it just stays there. let's say we have 2*2, the gradient tells us that you would have to subtract by 2 to get to go back once a term, 2*2 = 4, 2*1 = 2, the difference is 2 and the gradient has told us the difference, now what happens when we have squares, when both the incrementor and the gradient increases, 0*0 = 0, 1*1 indicates a difference of 1 so it is equal to 1, 2*2 indicates a difference of 2 from the last term of the sequence so it is 3 (1+2=3)