OFFSET
0,2
COMMENTS
a(n) = 3 if 2n+1 prime because the corresponding residues are 0, 1 and 2n (mod 2n+1).
LINKS
Amiram Eldar, Table of n, a(n) for n = 0..10000
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
KEYWORD
nonn
AUTHOR
Michel Lagneau, Oct 20 2011
STATUS
approved