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

1,2

Links

Table of n, a(n) for n=1..96.

Example

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

Mathematica

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

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).

Sequence in context: A378644 A083254 A068453 * A368744 A291455 A248849

Adjacent sequences: A111983 A111984 A111985 * A111987 A111988 A111989

Keyword

nonn

Author

T. D. Noe, Aug 25 2005

Status

approved