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A322436
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Number of pairs of factorizations of n into factors > 1 where no factor of the second properly divides any factor of the first.
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6
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1, 1, 1, 3, 1, 3, 1, 5, 3, 3, 1, 8, 1, 3, 3, 11, 1, 8, 1, 8, 3, 3, 1, 18, 3, 3, 5, 8, 1, 12, 1, 15, 3, 3, 3, 31, 1, 3, 3, 18, 1, 12, 1, 8, 8, 3, 1, 39, 3, 8, 3, 8, 1, 18, 3, 18, 3, 3, 1, 42, 1, 3, 8, 33, 3, 12, 1, 8, 3, 12, 1, 67, 1, 3, 8, 8, 3, 12, 1, 39, 11
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OFFSET
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1,4
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LINKS
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EXAMPLE
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The a(12) = 8 pairs of factorizations:
(2*2*3)|(2*2*3)
(2*2*3)|(2*6)
(2*2*3)|(3*4)
(2*2*3)|(12)
(2*6)|(12)
(3*4)|(3*4)
(3*4)|(12)
(12)|(12)
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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]]}]];
divpropQ[x_, y_]:=And[x!=y, Divisible[x, y]];
Table[Length[Select[Tuples[facs[n], 2], !Or@@divpropQ@@@Tuples[#]&]], {n, 100}]
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CROSSREFS
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Cf. A000688, A001055, A050336, A265947, A281113, A294068, A303386, A305149, A305150, A305193, A317144, A322435, A322439, A322440, A322441, A322442.
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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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