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A104527
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Denominator of sum(1/(phi(k)sigma(k)),k=1..n), where phi(k) is the totient function and sigma(k) is the sum of the divisors function.
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1
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1, 3, 24, 168, 7, 168, 112, 1680, 21840, 65520, 65520, 16380, 32760, 21840, 29120, 902720, 8124480, 8124480, 1624896, 1624896, 3249792, 5416320, 59579520, 59579520, 59579520, 178738560, 178738560, 178738560, 178738560, 178738560
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OFFSET
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1,2
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COMMENTS
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The first 5 sums are: 1,4/3,35/24,257/168,11/7.
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LINKS
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EXAMPLE
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a(3)=24 because phi(1)*sigma(1)+phi(2)*sigma(2)+phi(3)*sigma(3)=1/(1*1)+1/(1*3)+1/(2*4)=35/24.
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MAPLE
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with(numtheory): a:=n->denom(sum(1/phi(k)/sigma(k), k=1..n)): seq(a(n), n=1..35);
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CROSSREFS
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KEYWORD
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frac,nonn
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AUTHOR
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STATUS
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approved
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