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A330991
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Positive integers whose number of factorizations into factors > 1 (A001055) is a prime number (A000040).
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17
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4, 6, 8, 9, 10, 14, 15, 16, 21, 22, 24, 25, 26, 27, 30, 32, 33, 34, 35, 38, 39, 40, 42, 46, 49, 51, 54, 55, 56, 57, 58, 60, 62, 64, 65, 66, 69, 70, 74, 77, 78, 81, 82, 84, 85, 86, 87, 88, 90, 91, 93, 94, 95, 96, 102, 104, 105, 106, 110, 111, 114, 115, 118, 119
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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Factorizations of selected terms:
(4) (8) (16) (24) (60) (96)
(2*2) (2*4) (2*8) (3*8) (2*30) (2*48)
(2*2*2) (4*4) (4*6) (3*20) (3*32)
(2*2*4) (2*12) (4*15) (4*24)
(2*2*2*2) (2*2*6) (5*12) (6*16)
(2*3*4) (6*10) (8*12)
(2*2*2*3) (2*5*6) (2*6*8)
(3*4*5) (3*4*8)
(2*2*15) (4*4*6)
(2*3*10) (2*2*24)
(2*2*3*5) (2*3*16)
(2*4*12)
(2*2*3*8)
(2*2*4*6)
(2*3*4*4)
(2*2*2*12)
(2*2*2*2*6)
(2*2*2*3*4)
(2*2*2*2*2*3)
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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], PrimeQ[Length[facs[#]]]&]
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CROSSREFS
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Numbers whose number of strict integer partitions is prime are A035359.
Numbers whose number of integer partitions is prime are A046063.
Numbers whose number of set partitions is prime are A051130.
Numbers whose number of factorizations is a power of 2 are A330977.
The least number with prime(n) factorizations is A330992(n).
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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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