7 is the sole selection D for which the equation 2n − D = x2 has over two solutions for n and x natural. Especially, the equation 2n − 7 = x2 is named the Ramanujan–Nagell equation. By contrast, when you click on a Microsoft-furnished advert that seems on DuckDuckGo, https://spiroc048gsd6.wikigiogio.com/user