seven is the one number D for which the equation 2n ? D = x2 has over two methods for n and x natural. Particularly, the equation 2n ? 7 = x2 is recognized as the Ramanujan–Nagell equation.The island of Ogygia was the house of the beautiful nymph named Calypso. She fell madly in love with Odysseus and promised him immortality and eternal youth if… Read More