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A347946 Products of nonprimitive roots of n, or 0 if n = 2 or has no primitive roots. 0
0, 0, 1, 2, 4, 24, 48, 0, 4032, 17280, 5400, 0, 518400, 415134720, 0, 0, 1797120, 6467044147200, 39086530560, 0, 0, 1738201006080000, 10247897088, 0, 9632530575360000, 706822057112371200000, 569299069913333760000, 0, 54538738974720000, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
If n is a prime p, a(n) == -1 (mod p) for n > 3; if n is a composite c, a(n) == 0 (mod c) for n > 4.
LINKS
EXAMPLE
a(11) = 5400 because the primitive roots of 11 are {2,6,7,8} and therefore the nonprimitive roots of 11 are {1,3,4,5,9,10} and 1*3*4*5*9*10 = 5400.
MATHEMATICA
a[n_] := If[n == 2 || (p = PrimitiveRootList[n]) == {}, 0, (n - 1)!/Times @@ p]; Array[a, 30] (* Amiram Eldar, Sep 26 2021 *)
CROSSREFS
Sequence in context: A163896 A350813 A262698 * A168054 A280075 A068506
KEYWORD
nonn
AUTHOR
Davide Rotondo, Sep 26 2021
STATUS
approved

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Last modified April 18 22:18 EDT 2024. Contains 371782 sequences. (Running on oeis4.)