>
|
|
Numbers congruent to a perfect square are always quadratic residues. The converse is true as well.
>
|
|
>
|
|
is a quadratic residue modulo .
>
|
|
is not a quadratic residue modulo .
>
|
|
>
|
|
In the following plot, for each row index i and column index j, if the box indexed by i and j is black then j is a quadratic residue modulo i. If the box is white then j is a quadratic non-residue modulo i.
>
|
|
>
|
|