I'm not sure why you're using n as a loop iterator. I see nothing that says n should be a loop iterator. It looks like n should be a constant as far as I can see. It looks like the looping is only over the j variable, not n.
I also don't know what "x sub j" means. Is that the jth element of a vector x? Do you have multiple variables with different names, like x3, x4, x5, x6, ... xn?
And I don't know what the square brackets mean. Do they enclose indexes? Like xj[(j-1)*(j-2)] would be the row of xj that [(j-1)*(j-2)] evaluates to? Or are you taking the array xj (say x3 or x4 or whatever) and multiplying by the scalar [(j-1)*(j-2)] and dividing by the scalar [(n-1)*(n-2)]? It's tough to tell when you're not using standard MATLAB syntax.
So let's say j is 3 and n is 20. Is the sum x20 * [(3-1)*(3-2)] / [(20-1)*(20-2)], which equals x20 * [2*1] / [19*18] which equals x20 * 2/342?
