7 is the one range D for which the equation 2n − D = x2 has greater than two methods for n and x purely natural. Particularly, the equation 2n − 7 = x2 is known as the Ramanujan–Nagell equation. 2 hrs in the past By Mashable Team A MacBook https://louisyzuma.bmswiki.com/5590803/5_essential_elements_for_7_day_pill_organizers