Editing Quadratic residue (section)

===Quadratic excess===
Let ''p'' be an odd prime.  The '''quadratic excess''' ''E''(''p'') is the number of quadratic residues on the range (0,''p''/2) minus the number in the range (''p''/2,''p'') {{OEIS|A178153}}.  For ''p'' congruent to 1 mod 4, the excess is zero, since −1 is a quadratic residue and the residues are symmetric under ''r'' ↔ ''p''−''r''.  For ''p'' congruent to 3 mod 4, the excess ''E'' is always positive.<ref>{{cite book | first1=Paul T. | last1=Bateman | author1-link=Paul T. Bateman | first2=Harold G. | last2=Diamond | title=Analytic Number Theory | publisher=World Scientific | year=2004 | isbn=981-256-080-7 | zbl=1074.11001 | page=250 }}</ref>