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A211178
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Denominator of Sum_{k=1..n}(-1)^k/phi(k), where phi = A000010.
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4
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1, 1, 2, 1, 4, 4, 12, 3, 6, 12, 60, 30, 60, 20, 40, 20, 80, 240, 720, 720, 720, 144, 1584, 1584, 7920, 7920, 7920, 7920, 55440, 55440, 11088, 5544, 27720, 55440, 55440, 55440, 55440, 6160, 18480, 2310, 9240, 9240, 3080, 3080, 1155, 210, 2415, 38640, 5520, 5520
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OFFSET
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1,3
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LINKS
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FORMULA
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A211177(n)/a(n) = c*log(n) + O(1) with a suitable constant c (see ref).
The constant above is c = zeta(2)*zeta(3)/(3*zeta(6)) = (1/3) * A082695. - Amiram Eldar, Nov 20 2020
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MATHEMATICA
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Denominator @ Accumulate[Table[(-1)^k/EulerPhi[k], {k, 1, 50}]] (* Amiram Eldar, Nov 20 2020 *)
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PROG
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(PARI) a(n)=denominator(sum(k=1, n, (-1)^k/eulerphi(k)))
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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