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A073255
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Sum of divisors of n-th composite number.
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17
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7, 12, 15, 13, 18, 28, 24, 24, 31, 39, 42, 32, 36, 60, 31, 42, 40, 56, 72, 63, 48, 54, 48, 91, 60, 56, 90, 96, 84, 78, 72, 124, 57, 93, 72, 98, 120, 72, 120, 80, 90, 168, 96, 104, 127, 84, 144, 126, 96, 144, 195, 114, 124, 140, 96, 168, 186, 121, 126, 224, 108, 132
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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First composite is 4, sigma[4]=1+2+4=7=a(1).
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MAPLE
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map(numtheory:-sigma, remove(isprime, [$4..100])); # Robert Israel, Aug 27 2018
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MATHEMATICA
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c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Table[DivisorSigma[1, c[w]], {w, 1, 128}]
DivisorSigma[1, #]&/@(Select[Range[100], CompositeQ]) (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 10 2019 *)
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PROG
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(PARI) lista(nn) = forcomposite(c=1, nn, print1(sigma(c), ", ")); \\ Michel Marcus, Feb 21 2016
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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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