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-1, -2, -2, -2, -2, -4, -2, 0, 0, -4, -2, 0, -2, -4, 2, 8, -2, 0, -2, 8, 6, -4, -2, 16, 10, -4, 18, 16, -2, 4, -2, 32, 14, -4, 26, 36, -2, -4, 18, 48, -2, 12, -2, 32, 54, -4, -2, 64, 28, 20, 26, 40, -2, 36, 50, 80, 30, -4, -2, 72, -2, -4, 90, 96, 62, 28, -2, 56, 38, 52, -2, 144, -2, -4, 90, 64, 86, 36, -2, 160, 108, -4, -2, 120, 86, -4
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OFFSET
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1,2
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COMMENTS
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It can be shown that phi(n)*tau(n) >= n, which means that quotient = n/tau(n) <= phi(n); note: a(n)+5 is positive.
The value is always positive except when a(n)=0 for {8,9,12}; or a(n)=-2 for primes together with 4 (i.e., for A046022 but without 1); or a(n)=-4 for A001747 (without 2 and 4); or a(n)=-1 for n=1.
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LINKS
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MATHEMATICA
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Table[EulerPhi[n]DivisorSigma[0, n]-2n, {n, 90}] (* Harvey P. Dale, Feb 03 2021 *)
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PROG
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(PARI) a(n)={eulerphi(n)*numdiv(n) - 2*n} \\ Harry J. Smith, Aug 11 2009
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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