A111988 - OEIS

A111988

Greatest number having n quadratic residues, or 0 if there is no such number.

1, 4, 8, 16, 0, 24, 32, 48, 40, 19, 27, 80, 0, 96, 29, 144, 0, 120, 37, 76, 160, 108, 128, 240, 0, 0, 136, 288, 0, 152, 81, 336, 216, 67, 0, 360, 73, 148, 0, 304, 0, 480, 0, 432, 232, 384, 0, 720, 416, 0, 101, 103, 125, 440, 109, 672, 296, 0, 0, 464, 0, 324, 544, 1008, 0

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..65.

EXAMPLE

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

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, Last[pos]], {n, 100}]

CROSSREFS

Cf. A037046 (n such that a(n)=0), A111986 (number of numbers having n quadratic residues), A111987 (least number having n quadratic residues).

Sequence in context: A103536 A011970 A074025 * A361667 A361664 A110652

Adjacent sequences: A111985 A111986 A111987 * A111989 A111990 A111991

KEYWORD

nonn

AUTHOR

T. D. Noe, Aug 25 2005

STATUS

approved