Seven is the only amount D for which the equation 2n − D = x2 has a lot more than two methods for n and x pure. Particularly, the equation 2n − 7 = x2 is referred to as the Ramanujan–Nagell equation. Polynices was on the list of seven commanders. https://senioraidtools.com/10-easy-mobility-exercises-for-seniors-to-stay-active-and-independent/