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A146747
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Numbers k such that sigma_1(k)*sigma_0(k)/(sigma_1(k)-sigma_0(k)) is an integer.
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1
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OFFSET
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1,1
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COMMENTS
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LINKS
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MATHEMATICA
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q[n_] := Module[{s = DivisorSigma[1, n], d = DivisorSigma[0, n]}, Divisible[s*d, s - d]]; Select[Range[2, 100], q] (* Amiram Eldar, Apr 07 2024 *)
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PROG
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(PARI) is(n) = {my(f = factor(n), s = sigma(f), d = numdiv(f)); n > 1 && !((s*d) % (s-d)); } \\ Amiram Eldar, Apr 07 2024
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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