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A223608
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Numbers n whose deficiency is 18: sigma(n) - 2*n = -18.
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7
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OFFSET
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1,1
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COMMENTS
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a(6) > 10^12.
Any term x of this sequence can be combined with any term y of A223610 to satisfy the property (sigma(x)+sigma(y))/(x+y) = 2, which is a necessary (but not sufficient) condition for two numbers to be amicable. - Timothy L. Tiffin, Sep 13 2016
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LINKS
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EXAMPLE
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n = 33624064. sigma(n)-2*n = -18.
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MATHEMATICA
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Select[Range[1, 10^8], DivisorSigma[1, #] - 2 # == - 18 &] (* Vincenzo Librandi, Sep 14 2016 *)
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PROG
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(PARI) for(n=1, 10^8, if(sigma(n)-2*n==-18, print1(n ", ")))
(Magma) [n: n in [1..9*10^6] | (SumOfDivisors(n)-2*n) eq -18]; // Vincenzo Librandi, Sep 14 2016
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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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EXTENSIONS
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STATUS
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approved
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