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A061366
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Numbers k such that phi(k)+sigma(k) is a perfect cube.
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1
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99, 814, 1371, 2047, 2883, 5816, 6105, 6851, 10718, 16744, 19390, 19651, 20080, 20115, 20820, 22015, 22165, 22550, 23035, 25976, 30090, 31999, 32130, 34479, 36492, 36865, 37043, 39942, 40347, 42591, 44475, 48667, 52377, 54213, 54321
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OFFSET
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1,1
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LINKS
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EXAMPLE
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phi(99)+sigma(99) = 60+156 = 216 = 6^3, so 99 is a term of the sequence.
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MATHEMATICA
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Select[Range[10^5], IntegerQ[(EulerPhi[ # ] + DivisorSigma[1, # ])^(1/3)] &]
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PROG
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(PARI) isok(n) = ispower(eulerphi(n)+sigma(n), 3); \\ Michel Marcus, Sep 28 2019
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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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