Seven is the only real number D for which the equation 2n − D = x2 has in excess of two solutions for n and x pure. Specifically, the equation 2n − 7 = x2 is referred to as the Ramanujan–Nagell equation. 2 hours ago By Mashable Crew A MacBook https://marcoleuiu.wiki-jp.com/1819686/5_simple_statements_about_7_day_pill_organizers_explained