A111986 Number of numbers having n quadratic residues.

1, 3, 2, 5, 0, 5, 2, 6, 2, 1, 2, 12, 0, 4, 1, 6, 0, 6, 1, 3, 4, 7, 1, 17, 0, 0, 3, 7, 0, 6, 2, 6, 3, 1, 0, 15, 1, 3, 0, 6, 0, 11, 0, 14, 3, 1, 0, 24, 2, 0, 1, 1, 1, 10, 1, 8, 3, 0, 0, 13, 0, 5, 5, 7, 0, 10, 0, 3, 2, 3, 0, 26, 0, 3, 1, 6, 4, 0, 2, 9, 3, 1, 0, 25, 0, 0, 2, 18, 0, 13, 1, 3, 4, 0, 0, 26

Offset: 1

Author

T. D. Noe, Aug 25 2005

Keywords

• nonn

Examples

			a(4)=5 because the numbers 6, 7, 9, 12 and 16 each have 4 quadratic residues.
		

Crossrefs

Cf. A037041 (n such that a(n)>0), A037046 (n such that a(n)=0), A111987 (least number having n quadratic residues), A111988 (greatest number having n quadratic residues).

Programs

Mathematica

t=Table[Length[Union[Mod[Range[0, n/2]^2, n]]], {n, 10000}]; Table[Length[Position[t, n]], {n, 100}]