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A327907
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Numbers with more than one factorization into at factors > 1 with integer mean.
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1
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4, 8, 9, 12, 15, 16, 20, 21, 24, 25, 27, 28, 32, 33, 35, 36, 39, 40, 42, 44, 45, 48, 49, 50, 51, 52, 54, 55, 56, 57, 60, 63, 64, 65, 68, 69, 72, 75, 76, 77, 78, 80, 81, 84, 85, 87, 88, 91, 92, 93, 95, 96, 99, 100, 104, 105, 108, 110, 111, 112, 114, 115, 116
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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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There are 6 factorizations of 60 with integer mean, namely:
(60)
(2*30)
(6*10)
(3*4*5)
(2*3*10)
(2*2*3*5)
so 60 is in the sequence.
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MATHEMATICA
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facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Select[Range[100], Length[Select[facs[#], IntegerQ[Mean[#]]&]]>1&]
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CROSSREFS
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Cf. A001055, A051293, A067538, A078175, A123528/A123529, A316413, A326515, A326516, A326666, A326667, A326671.
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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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