Source: wikibot/idoneal-number
= Idoneal number
{wiki=Idoneal_number}
An Idoneal number is a positive integer \\( n \\) such that the equation \\( x^2 - n y^2 = 1 \\) has a solution in integers \\( (x, y) \\). This is a specific case of Pell's equation, which is generally of the form \\( x^2 - D y^2 = 1 \\) for some positive integer \\( D \\).