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A307869
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Decimal expansion of the asymptotic mean of d(k)/2^omega(k), where d(k) is the number of divisors of k (A000005) and omega(k) is the number of its distinct prime divisors (A001221).
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9
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1, 4, 2, 7, 6, 5, 6, 5, 3, 5, 4, 2, 4, 8, 3, 9, 8, 8, 3, 1, 1, 7, 5, 2, 3, 9, 3, 9, 6, 8, 7, 3, 2, 7, 9, 0, 4, 0, 9, 3, 7, 3, 3, 6, 2, 8, 0, 7, 4, 4, 3, 9, 2, 7, 4, 2, 2, 4, 7, 4, 1, 4, 3, 6, 7, 3, 4, 4, 2, 9, 8, 8, 3, 4, 1, 1, 5, 3, 8, 9, 4, 0, 7, 4, 8, 3, 0, 3, 5, 2, 6, 0, 8, 3, 7, 4, 0, 5, 1, 7, 7, 9, 3, 2, 5
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OFFSET
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1,2
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COMMENTS
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Also the asymptotic mean of ratio between the number of divisors and the number of unitary divisors of the integers.
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LINKS
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FORMULA
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Equals Product_{p prime} 1 + 1/(2 * p * (p-1)).
Equals (Pi^2/6) * Product_{p prime} 1 - 1/(2 * p^2) + 1/(2 * p^3).
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EXAMPLE
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1.42765653542483988311752393968732790409373362807443...
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MATHEMATICA
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$MaxExtraPrecision = 1000; m = 1000; c = LinearRecurrence[{4, -6, 4}, {0, 4, 12}, m]; RealDigits[Exp[NSum[Indexed[c, n]*PrimeZetaP[n]/n/2^n, {n, 2, m}, NSumTerms -> m, WorkingPrecision -> m]], 10, 100][[1]]
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PROG
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(PARI) prodeulerrat(1 + 1/(2 * p * (p-1))) \\ Amiram Eldar, Mar 17 2021
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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