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A141677
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Numbers of the functional form: a(n)=DivisorSigma[0, n]*PrimePi[n].
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0
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0, 2, 4, 6, 6, 12, 8, 16, 12, 16, 10, 30, 12, 24, 24, 30, 14, 42, 16, 48, 32, 32, 18, 72, 27, 36, 36, 54, 20, 80, 22, 66, 44, 44, 44, 99, 24, 48, 48, 96, 26, 104, 28, 84, 84, 56, 30, 150, 45, 90, 60, 90, 32, 128, 64, 128, 64, 64, 34, 204, 36, 72, 108, 126, 72, 144, 38, 114, 76
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Only five in the first 200 integers give odd values for this function:
Flatten[Table[If[Mod[DivisorSigma[0, n]*PrimePi[n], 2] == 1, n, {}], {n, 1, 200}]]
{25, 36, 49, 100, 169}.
This sort of functional modulo categorization of Integers appears to be new.
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FORMULA
| a(n)=DivisorSigma[0, n]*PrimePi[n].
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MATHEMATICA
| Table[DivisorSigma[0, n]*PrimePi[n], {n, 1, 100}]
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CROSSREFS
| Sequence in context: A060685 A073353 A066820 * A087459 A123258 A104968
Adjacent sequences: A141674 A141675 A141676 * A141678 A141679 A141680
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KEYWORD
| nonn,uned
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AUTHOR
| Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Sep 07 2008
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