In number theory concerning primes
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 be an integer coprime to p. Then[1][2][3]
Euler's criterion can be concisely reformulated using the Legendre symbol:[4]
The criterion dates from a 1748 paper by Leonhard Euler.[5][6]
- ^ Gauss, DA, Art. 106
- ^ Dense, Joseph B.; Dence, Thomas P. (1999). "Theorem 6.4, Chap 6. Residues". Elements of the Theory of Numbers. Harcourt Academic Press. p. 197. ISBN 9780122091308.
- ^ Leonard Eugene Dickson, "History Of The Theory Of Numbers", vol 1, p 205, Chelsea Publishing 1952
- ^ Hardy & Wright, thm. 83
- ^ Lemmermeyer, p. 4 cites two papers, E134 and E262 in the Euler Archive
- ^ L Euler, Novi commentarii Academiae Scientiarum Imperialis Petropolitanae, 8, 1760-1, 74; Opusc Anal. 1, 1772, 121; Comm. Arith, 1, 274, 487