At first glance this:
doesn’t make much sense. Most likely what you wanted to write was this:
Vector3(5 * j * cos (360 / 80 * i), 1, 5 * j * sin (360 / 80 * i));
I.e. first radius is 5 * j you’ve had 5 * i instead
Next you have i outside of sin/cos argument, to have a “circle” you need sin(k * i).