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A198020 Number of distinct residues of x^n (mod 2n+1), x=0..2n. 2
1, 3, 3, 3, 4, 3, 3, 15, 3, 3, 8, 3, 6, 19, 3, 3, 12, 35, 3, 39, 3, 3, 12, 3, 8, 51, 3, 55, 20, 3, 3, 49, 8, 3, 24, 3, 3, 63, 24, 3, 28, 3, 27, 87, 3, 15, 32, 95, 3, 77, 3, 3, 16, 3, 3, 111, 3, 115, 28, 119, 12, 123, 51, 3, 44, 3, 8, 95, 3, 3, 48, 143, 16, 129 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n) = 3 if 2n+1 prime because the corresponding residues are 0, 1 and 2n (mod 2n+1).

LINKS

Table of n, a(n) for n=0..73.

EXAMPLE

a(7) = 15 because x^7  == 0, 1, …,14  (mod 15) => 15 distinct residues.

MATHEMATICA

Table[Length[Union[PowerMod[Range[0, 2*n], n, 2*n+1]]], {n, 0, 100}]

CROSSREFS

Cf. A195637, A197929.

Sequence in context: A010265 A239963 A084501 * A098037 A079108 A165605

Adjacent sequences:  A198017 A198018 A198019 * A198021 A198022 A198023

KEYWORD

nonn

AUTHOR

Michel Lagneau, Oct 20 2011

STATUS

approved

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Last modified March 24 12:14 EDT 2019. Contains 321448 sequences. (Running on oeis4.)