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Search: id:A091896
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| A091896 |
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Numbers n such that there exists no k for which the denominator of d(k)/k = n. |
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+0
2
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| 18, 30, 72, 112, 144, 243, 252, 288, 294, 336, 360, 396, 468, 504, 576, 612, 616, 625, 684, 726, 728, 792, 810, 828, 840, 936, 952, 960, 1014, 1044, 1064, 1116, 1224, 1250, 1260, 1288, 1332, 1350, 1368, 1386, 1440, 1476, 1548, 1568, 1584, 1624, 1638, 1656
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OFFSET
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1,1
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COMMENT
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The number of zeros <= 10^n: 0,3,28,311,
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MATHEMATICA
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a = Table[0, {2000}]; Do[m = n; b = Denominator[ DivisorSigma[0, n]/n]; If[b < 2001 && a[[b]] == 0, a[[b]] = n], {n, 1, 25000000}]; Select[ Range[2000], a[[ # ]] == 0 &]
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CROSSREFS
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Cf. A090395, the zeros of A091895.
Sequence in context: A043143 A043923 A160916 this_sequence A101140 A070744 A137600
Adjacent sequences: A091893 A091894 A091895 this_sequence A091897 A091898 A091899
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 09 2004
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