7 is the only real selection D for which the equation 2n − D = x2 has more than two methods for n and x purely natural. In particular, the equation 2n − 7 = x2 is referred to as the Ramanujan–Nagell equation.Not All people thinks that cats have 9 life. In some areas of Spain, Germany, and Iran, it’s claimed that cats have just 7 life! I pon