7 is the only real quantity D for which the equation 2n − D = x2 has in excess of two alternatives for n and x natural. Specifically, the equation 2n − 7 = x2 is known as the Ramanujan–Nagell equation. Jahannam has seven gates which are open up constantly. https://angeloyrhsd.bloguerosa.com/36652733/how-7-day-pill-organizers-can-save-you-time-stress-and-money