7 is the only amount D for which the equation 2n − D = x2 has in excess of two solutions for n and x all-natural. In particular, the equation 2n − seven = x2 is named the Ramanujan–Nagell equation. Jahannam has seven gates that are open constantly. (Qur’an – https://bullc621fkc3.elbloglibre.com/profile