login
A111986
Number of numbers having n quadratic residues.
3
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
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: A085015 A083254 A068453 * A368744 A291455 A248849
KEYWORD
nonn
AUTHOR
T. D. Noe, Aug 25 2005
STATUS
approved