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A059889
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a(n) = |{m : multiplicative order of 7 mod m=n}|.
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16
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4, 6, 8, 26, 4, 42, 12, 48, 52, 66, 12, 778, 4, 138, 80, 300, 12, 528, 12, 1430, 72, 138, 28, 15216, 24, 66, 1216, 966, 28, 3630, 28, 1344, 360, 58, 108, 16988, 28, 138, 176, 12752, 28, 7398, 12, 4422, 1900, 122, 12, 131028, 240, 536, 744, 1046, 28, 23744, 44
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OFFSET
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1,1
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COMMENTS
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The multiplicative order of a mod m, gcd(a,m)=1, is the smallest natural number d for which a^d = 1 (mod m).
a(n) = number of orders of degree n monic irreducible polynomials over GF(7).
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LINKS
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FORMULA
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a(n) = Sum_{d|n} mu(n/d)*tau(7^d-1), (mu(n) = Moebius function A008683, tau(n) = number of divisors of n A000005).
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MAPLE
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with(numtheory):
a:= n-> add(mobius(n/d)*tau(7^d-1), d=divisors(n)):
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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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