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A111988 Greatest number having n quadratic residues, or 0 if there is no number. 3
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 (list; graph; refs; listen; history; text; internal format)
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: A321500 A103536 A011970 * A110652 A059373 A137798

Adjacent sequences:  A111985 A111986 A111987 * A111989 A111990 A111991

KEYWORD

nonn

AUTHOR

T. D. Noe, Aug 25 2005

STATUS

approved

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Last modified February 20 16:42 EST 2020. Contains 332080 sequences. (Running on oeis4.)