Pell's equation

Etymology
Named by Leonhard Euler after the 17th-century mathematician John Pell, whom Euler mistakenly believed to be the first to find a general solution.

Noun

 * 1)  The Diophantine equation $$x^2 - my^2 = 1$$ for a given integer m, to be solved in integers x and y.

Translations

 * German: Pellsche Gleichung
 * Italian: equazione di Pell