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A239161
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Numbers n such that the ratio (sum of divisors of n) /(sum of divisors d of n with d <= sqrt(n)) is an integer.
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2
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1, 2, 3, 5, 6, 7, 8, 10, 11, 13, 14, 15, 17, 19, 20, 21, 22, 23, 24, 26, 27, 28, 29, 31, 32, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 46, 47, 51, 52, 53, 54, 55, 57, 58, 59, 60, 61, 62, 65, 66, 67, 68, 69, 71, 73, 74, 76, 77, 78, 79, 82, 83, 85, 86, 87, 88, 89
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OFFSET
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1,2
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COMMENTS
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The corresponding integers are in A238502.
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LINKS
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EXAMPLE
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13 is in the sequence because A000203(13)/A066839(13) = 14/1 = 14 is an integer.
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MATHEMATICA
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lst={}; f[n_]:=DivisorSigma[1, n]/Plus@@Select[Divisors@n, #<=Sqrt@n&]; Do[If[IntegerQ[f[n]], AppendTo[lst, n]], {n, 1, 200}]; lst
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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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