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A015729
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Numbers n such that phi(n) * sigma(n) + 16 is a perfect square.
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2
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7, 21, 32, 46, 60, 77, 123, 124, 132, 221, 224, 254, 261, 287, 308, 312, 376, 437, 445, 506, 534, 539, 665, 680, 717, 752, 770, 798, 860, 948, 1239, 1264, 1340, 1517, 1519, 1617, 1628, 1815, 2021, 2275, 2288, 2320, 2379, 2400, 2871, 2890
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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Select[Range[3000], IntegerQ[Sqrt[EulerPhi[#]DivisorSigma[1, #]+16]]&] (* Harvey P. Dale, Dec 07 2012 *)
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PROG
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(Magma) [n: n in [1..3000] | IsSquare(EulerPhi(n) * SumOfDivisors(n)+16)]; // Vincenzo Librandi, Mar 14 2014
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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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