A111987 Least number having n quadratic residues, or 0 if there is no number.

1, 2, 5, 6, 0, 10, 13, 14, 17, 19, 25, 22, 0, 26, 29, 31, 0, 34, 37, 38, 41, 43, 128, 46, 0, 0, 53, 78, 0, 58, 61, 62, 135, 67, 0, 71, 73, 74, 0, 79, 0, 82, 0, 86, 89, 384, 0, 94, 97, 0, 101, 103, 125, 106, 109, 121, 113, 0, 0, 118, 0, 122, 205, 127, 0, 131, 0, 134, 137, 139, 0

Offset

1,2

Links

Table of n, a(n) for n=1..71.

Example

a(4)=6 because, of the five numbers having 4 quadratic residues (6,7,9,12,16), the least is 6.

Mathematica

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

Crossrefs

Cf. A037046 (n such that a(n)=0), A111986 (number of numbers having n quadratic residues), A111988 (greatest number having n quadratic residues).

Sequence in context: A127598 A196550 A011037 * A004650 A138279 A131800

Adjacent sequences: A111984 A111985 A111986 * A111988 A111989 A111990

Keyword

nonn

Author

T. D. Noe, Aug 25 2005

Status

approved