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A131089
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a(n) = Sum_{d|n} (2 - mu(d)).
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1
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1, 4, 4, 6, 4, 8, 4, 8, 6, 8, 4, 12, 4, 8, 8, 10, 4, 12, 4, 12, 8, 8, 4, 16, 6, 8, 8, 12, 4, 16, 4, 12, 8, 8, 8, 18, 4, 8, 8, 16, 4, 16, 4, 12, 12, 8, 4, 20, 6, 12, 8, 12, 4, 16, 8, 16, 8, 8, 4, 24, 4, 8, 12, 14, 8, 16, 4, 12, 8, 16, 4, 24, 4, 8, 12, 12, 8, 16
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Inverse Moebius transform of A228483.
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EXAMPLE
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a(4) = 6 = (2 + 3 + 0 + 1), row 4 of A131088.
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MATHEMATICA
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Join[{1}, Table[2 DivisorSigma[0, n], {n, 100}]] (* Vincenzo Librandi, Aug 10 2018 *)
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PROG
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(Magma) [1] cat [2*NumberOfDivisors(n) : n in [2..100] ]; // Vincenzo Librandi, Aug 10 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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EXTENSIONS
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Name changed and terms a(10) and beyond from Andrew Howroyd, Aug 09 2018
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STATUS
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approved
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