KnowraFermat's theorem on sums of two squaresLinked fromLinked fromThe 6 pages that link to Fermat's theorem on sums of two squares, each with the reason it gives.All 6Broader topic 1Related 4Compared with 1Lagrange's four-square theoremCompared with: Its residue restriction contrasts with the four-square theorem's representation of every prime.Fermat numberRelated: Every odd prime divisor of a Fermat number is congruent to 1 modulo a power of two, hence is a sum of two squares.Infinite descentRelated: Descent arguments appear in classical work surrounding representations by sums of squares.Sum of two squares theoremBroader topic: The prime case supplies the central building block of the full criterion.Euler's four-square identityRelated: It concerns the arithmetic family whose multiplication law is the two-square analogue.Brahmagupta–Fibonacci identityRelated: The identity helps combine prime representations into representations of composite numbers.