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A175433
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a(n) = the smallest number m such that sigma(n) = m^k for any k >= 1 (sigma = A000203).
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2
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1, 3, 2, 7, 6, 12, 2, 15, 13, 18, 12, 28, 14, 24, 24, 31, 18, 39, 20, 42, 2, 6, 24, 60, 31, 42, 40, 56, 30, 72, 2, 63, 48, 54, 48, 91, 38, 60, 56, 90, 42, 96, 44, 84, 78, 72, 48, 124, 57, 93, 72, 98, 54, 120, 72, 120, 80, 90, 60, 168, 62, 96, 104, 127, 84, 12, 68, 126, 96, 12
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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For n = 7, a(7) = 2 because sigma(7) = 8 = 2^3.
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MATHEMATICA
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Array[#^(1/Apply[GCD, FactorInteger[#][[All, -1]]]) &@ DivisorSigma[1, #] &, 105] (* Michael De Vlieger, Nov 05 2017 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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