Seven is the only real range D for which the equation 2n − D = x2 has a lot more than two methods for n and x natural. Particularly, the equation 2n − 7 = x2 is named the Ramanujan–Nagell equation. Not All people thinks that cats have nine life. https://senioraidtools.com/10-easy-mobility-exercises-for-seniors-to-stay-active-and-independent/