Which condition is sufficient for x2+y2=nx^2 + y^2 = nx2+y2=n to have exactly 8 integer solutions?
n=52n = 5^2n=52
n=2×5n = 2 \times 5n=2×5
n=13n = 13n=13
n=2×13n = 2 \times 13n=2×13