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A064596
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Smallest nonunitary multiperfect number of index n; i.e., smallest k such that sigma(k) - usigma(k) = nk.
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5
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OFFSET
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0,2
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COMMENTS
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4.5*10^14 < a(4) <= 1081895452249824576000.
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LINKS
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MATHEMATICA
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nusigma[ n_ ] := DivisorSigma[ 1, n ]-Times@@(1+Power@@#&/@FactorInteger[ n ]); a[ n_ ] := For[ k=1, True, k++, If[ nusigma[ k ]==n k, Return[ k ] ] ]
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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STATUS
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approved
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