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A345674
Euler totient function phi(n) - number of primitive roots modulo n.
0
0, 0, 1, 1, 2, 1, 4, 4, 4, 2, 6, 4, 8, 4, 8, 8, 8, 4, 12, 8, 12, 6, 12, 8, 12, 8, 12, 12, 16, 8, 22, 16, 20, 8, 24, 12, 24, 12, 24, 16, 24, 12, 30, 20, 24, 12, 24, 16, 30, 12, 32, 24, 28, 12, 40, 24, 36, 16, 30, 16, 44, 22, 36, 32, 48, 20, 46, 32, 44, 24
OFFSET
1,5
FORMULA
a(n) = A000010(n) - A046144(n).
MAPLE
a:= proc(n) uses numtheory; `if`(n=1, 0, (p->
p-add(`if`(order(i, n)=p, 1, 0), i=0..n-1))(phi(n)))
end:
seq(a(n), n=1..70); # Alois P. Heinz, Jun 22 2021
MATHEMATICA
a[n_] := (e = EulerPhi[n]) - If[n == 1 || IntegerQ @ PrimitiveRoot[n], EulerPhi[e], 0]; Array[a, 100] (* Amiram Eldar, Jun 23 2021 *)
CROSSREFS
Sequence in context: A110316 A111975 A117250 * A296337 A308432 A136692
KEYWORD
nonn
AUTHOR
Robert Hutchins, Jun 22 2021
STATUS
approved