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A083540
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A083539[n] is a square; solutions x to sigma[x+1].sigma[x]=y^2 for some y.
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3
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14, 30, 51, 161, 186, 206, 223, 329, 552, 713, 759, 869, 957, 994, 995, 1248, 1334, 1364, 1634, 1715, 1819, 2093, 2133, 2584, 2685, 2820, 2821, 2974, 3115, 3145, 3485, 4212, 4308, 4312, 4364, 4408, 4649
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OFFSET
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1,1
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LINKS
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Harvey P. Dale, Table of n, a(n) for n = 1..1000
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EXAMPLE
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x=30: sigma[30]=72, sigma[31]=32,product=72.32=256.9=24^2
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MATHEMATICA
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Do[s=Sqrt[DivisorSigma[1, n+1]*DivisorSigma[1, n]]; If[IntegerQ[s], Print[n]], {n, 1, 5000}]
Flatten[Position[Times@@@Partition[DivisorSigma[1, Range[5000]], 2, 1], _?(IntegerQ[Sqrt[#]]&)]] (* Harvey P. Dale, Mar 07 2016 *)
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CROSSREFS
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Cf. A000203, A083539, A060780, A060781, A083538.
Sequence in context: A044456 A132759 A011257 * A027575 A104776 A308312
Adjacent sequences: A083537 A083538 A083539 * A083541 A083542 A083543
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KEYWORD
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nonn
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AUTHOR
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Labos Elemer, May 21 2003
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STATUS
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approved
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