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A218258
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a(n) = |{m : multiplicative order of n mod m = 9}|.
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2
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0, 2, 4, 26, 18, 12, 52, 4, 112, 12, 16, 12, 30, 12, 24, 488, 30, 24, 64, 4, 12, 78, 48, 28, 464, 12, 56, 62, 72, 12, 104, 56, 36, 52, 48, 112, 432, 28, 48, 52, 48, 24, 488, 56, 72, 288, 48, 24, 580, 6, 24, 116, 360, 44, 344, 16, 48, 104, 24, 8, 312, 44, 112
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = tau(n^9-1)-tau(n^3-1), with tau = A000005.
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MAPLE
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with(numtheory):
a:= n-> add(mobius(9/d) *tau(n^d-1), d={3, 9}):
seq(a(n), n=1..80);
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MATHEMATICA
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Table[DivisorSigma[0, n^9-1]-DivisorSigma[0, n^3-1], {n, 70}] (* Harvey P. Dale, Mar 15 2018 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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