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A330972
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Sorted list containing the least number with each possible nonzero number of factorizations into factors > 1.
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38
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1, 4, 8, 12, 16, 24, 36, 48, 60, 72, 96, 120, 128, 144, 180, 192, 216, 240, 256, 288, 360, 384, 420, 432, 480, 576, 720, 768, 840, 864, 900, 960, 1024, 1080, 1152, 1260, 1440, 1680, 1728, 1800, 1920, 2048, 2160, 2304, 2520, 2592, 2880, 3072, 3360, 3456, 3600
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OFFSET
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1,2
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COMMENTS
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This is the sorted list of positions of first appearances in A001055 of each element of the range (A045782).
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LINKS
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EXAMPLE
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Factorizations of n for n = 4, 8, 12, 16, 24, 36, 48, 60:
4 8 12 16 24 36 48 60
2*2 2*4 2*6 2*8 3*8 4*9 6*8 2*30
2*2*2 3*4 4*4 4*6 6*6 2*24 3*20
2*2*3 2*2*4 2*12 2*18 3*16 4*15
2*2*2*2 2*2*6 3*12 4*12 5*12
2*3*4 2*2*9 2*3*8 6*10
2*2*2*3 2*3*6 2*4*6 2*5*6
3*3*4 3*4*4 3*4*5
2*2*3*3 2*2*12 2*2*15
2*2*2*6 2*3*10
2*2*3*4 2*2*3*5
2*2*2*2*3
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MATHEMATICA
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nn=1000;
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
nds=Length/@Array[facs, nn];
Table[Position[nds, i][[1, 1]], {i, First/@Gather[nds]}]
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CROSSREFS
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Includes all highly factorable numbers A033833.
The least number with n factorizations is A330973(n).
Cf. A001222, A002033, A007716, A045778, A318284, A325238, A330935, A330936, A330976, A330977, A330989, A330991, A330992.
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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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