Seven is the one selection D for which the equation 2n − D = x2 has in excess of two alternatives for n and x purely natural. Particularly, the equation 2n − 7 = x2 is referred to as the Ramanujan–Nagell equation. Naturally there is also the nicely-regarded story of https://non-slipslippersforelderl91987.blogunok.com/37953739/the-7-day-pill-organizers-diaries