Quadratic residue
= Quadratic residue
{wiki}
For an odd prime $p$, a nonzero class $a$ is a quadratic residue when $a\equiv x^2\pmod p$. These residues form an index-two subgroup of $(\mathbb Z/p\mathbb Z)^\times$.
= Quadratic residue
{wiki}
For an odd prime $p$, a nonzero class $a$ is a quadratic residue when $a\equiv x^2\pmod p$. These residues form an index-two subgroup of $(\mathbb Z/p\mathbb Z)^\times$.