How to code variables in GA which are changing with in "for" loop

I want to minimze my function in which my x and y is depending on two other values i and j .x(i,,j) and y(j,k).So I am using "for" loops i and j and k for that. But i dont know how to define these values of x nd y in genetic algorithm function as ga takes x(1),x(2),x(3 ... as names of variables.For example my function is:

where x(i,j) and y(j,k) are my decision variable which should be changing for every value of i and j and k. Can I define them as x(i,j,(1)) and x(j,k(,2))? Though it gives me error