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A323090
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Number of strict factorizations of n using elements of A007916 (numbers that are not perfect powers).
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3
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1, 1, 1, 0, 1, 2, 1, 0, 0, 2, 1, 2, 1, 2, 2, 0, 1, 2, 1, 2, 2, 2, 1, 2, 0, 2, 0, 2, 1, 5, 1, 0, 2, 2, 2, 3, 1, 2, 2, 2, 1, 5, 1, 2, 2, 2, 1, 2, 0, 2, 2, 2, 1, 2, 2, 2, 2, 2, 1, 7, 1, 2, 2, 0, 2, 5, 1, 2, 2, 5, 1, 4, 1, 2, 2, 2, 2, 5, 1, 2, 0, 2, 1, 7, 2, 2, 2
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OFFSET
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1,6
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LINKS
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EXAMPLE
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The a(72) = 4 factorizations are (2*3*12), (3*24), (6*12), (72). Missing from this list and not strict are (2*2*2*3*3), (2*2*3*6), (2*6*6), (2*2*18), while missing from the list and using perfect powers are (2*36), (2*4*9), (3*4*6), (4*18), (8*9).
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MATHEMATICA
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radQ[n_]:=Or[n==1, GCD@@FactorInteger[n][[All, 2]]==1];
facssr[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facssr[n/d], Min@@#>d&]], {d, Select[Rest[Divisors[n]], radQ]}]];
Table[Length[facssr[n]], {n, 100}]
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CROSSREFS
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Cf. A001055, A001597, A007916, A025147, A045778, A052410, A303707, A323054, A323087, A323088, A323089.
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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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