- (
*a/n*) = (*b/n*) if*a*=*b*mod*n*. - (1/
*n*) = 1 and (0/*n*) = 0. - (2
*m*/*n*) = (*m/n*) if*n*= ±1 mod 8. Otherwise (2*m/n*) =_{¯}(*m/n*). - (
**Quadratic reciprocity**) If*m*and*n*are both odd, then (*m/n*) = (*n/m*) unless both*m*and*n*are congruent to 3 mod 4, in which case (*m/n*) =_{¯}(*n/m*).