In number theory Euler's criterion is a formula for determining whether an integer is a quadratic residue modulo a prime. Precisely,
Let p be an odd prime and a an integer coprime to p. Then
Euler's criterion can be concisely reformulated using the Legendre symbol:
The criterion first appeared in a 1748 paper by Euler.
Famous quotes containing the word criterion:
“I divide all literary works into two categories: Those I like and those I dont like. No other criterion exists for me.”
—Anton Pavlovich Chekhov (18601904)