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A331051
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Numbers whose number of factorizations into factors > 1 (A001055) is even.
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4
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4, 6, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 28, 33, 34, 35, 38, 39, 44, 45, 46, 48, 49, 50, 51, 52, 55, 57, 58, 62, 63, 65, 68, 69, 72, 74, 75, 76, 77, 80, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 106, 108, 111, 112, 115, 116, 117, 118, 119, 121, 122
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OFFSET
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1,1
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COMMENTS
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First differs from A319240 in having 256.
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LINKS
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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[300], EvenQ[Length[facs[#]]]&]
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CROSSREFS
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The version for powers of two (instead of evens) is A330977.
The version for primes (instead of evens) is A330991.
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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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