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A092588
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Numbers k such that sigma(phi(k)) - phi(sigma(k)) is nonzero and divisible by sigma(k), that is A065395(k)/A000203(k) is a nonzero integer.
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6
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7, 327, 463, 497, 617, 691, 751, 1207, 1633, 2451, 2643, 3143, 3337, 3503, 4939, 5609, 7093, 7597, 10327, 14987, 20427, 21103, 22345, 22481, 24739, 26491, 27193, 28077, 37753, 37915, 42711, 42717, 47647, 48043, 49243, 50071, 51727, 54823, 57478
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OFFSET
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1,1
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LINKS
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EXAMPLE
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(sigma(phi(x))-phi(sigma(x)))/sigma(x) quotient equals 1 for x=7, 2 for x=327, 3 for x=5609.
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MATHEMATICA
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fs[x_] := EulerPhi[DivisorSigma[1, x]] sf[x_] := DivisorSigma[1, EulerPhi[x]] {t=Table[0, {100}], j=1}; Do[s=(sf[n]-fs[n])/DivisorSigma[1, n]; If[ !Equal[s, 0]&&IntegerQ[s], Print[n]; t[[j]]=n; j=j+1], {n, 2, 1000000}] t
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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