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A087802
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a(n) = Sum_{d|n, d nonprime} mu(d), where mu = A008683.
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2
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1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 3, 1, 1, 2, 2, 2, 2, 1, 2, 2, 2, 1, 3, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 1, 3, 1, 2, 2, 1, 2, 3, 1, 2, 2, 3, 1, 2, 1, 2, 2, 2, 2, 3, 1, 2, 1, 2, 1, 3, 2, 2, 2, 2, 1, 3, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 1, 3
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OFFSET
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1,6
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COMMENTS
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LINKS
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FORMULA
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EXAMPLE
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Divisors of n=42: {1,2,3,6,7,14,21,42}, a(42) = mu(1) + mu(6) + mu(14) + mu(21) + mu(42) = 1+1+1+1-1 = 3.
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MATHEMATICA
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Table[Total[MoebiusMu[#]&/@Select[Divisors[n], !PrimeQ[#]&]], {n, 120}] (* Harvey P. Dale, Oct 14 2014 *)
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PROG
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(PARI) A087802(n) = sumdiv(n, d, if(!isprime(d), moebius(d)))
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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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