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Search: id:A143896
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| A143896 |
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Numbers that are among the d smallest numbers with d divisors. |
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+0
1
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| 1, 2, 3, 4, 6, 8, 9, 10, 12, 14, 16, 18, 20, 24, 25, 28, 30, 32, 36, 40, 42, 44, 48, 54, 56, 60, 64, 66, 70, 72, 80, 81, 84, 90, 96, 100, 108, 112, 120, 126, 132, 140, 144, 150, 156, 160, 162, 168, 176, 180, 192, 196, 208, 210, 216, 225, 240, 252, 256, 264, 270, 272, 280
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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15 does not qualify because it has 4 divisors and the 4 smallest numbers with 4 divisors are 6, 8, 10 and 14.
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MATHEMATICA
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ds[n_] := ds[n] = DivisorSigma[0, n]; fQ[n_] := Block[{d = ds@n}, MemberQ[ Select[ Range@n, Take[ DivisorSigma[0, # ] == d &], d], n]]; Select[ Range@ 299, fQ@# &] [From Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 09 2008]
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CROSSREFS
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Sequence in context: A068577 A035033 A054220 this_sequence A160719 A085451 A064150
Adjacent sequences: A143893 A143894 A143895 this_sequence A143897 A143898 A143899
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KEYWORD
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nonn
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AUTHOR
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J. Lowell (jhbubby(AT)mindspring.com), Sep 04 2008
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 09 2008
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