Euler's Quadratic Residue Theorem

A number D that possesses no common divisor with a prime number p is either a quadratic residue or nonresidue of p, depending whether D^((p-1)/2) is congruent mod p to +/-1.

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Cite this as:

Weisstein, Eric W. "Euler's Quadratic Residue Theorem." From MathWorld--A Wolfram Web Resource.

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