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Search: id:A087485
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| A087485 |
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Odd numbers n such that 2n-sigma(n)=6. |
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6
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OFFSET
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1,1
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COMMENT
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This is a subsequence of A077374. There are no others up to 2*10^9. Except for the first term all known terms of this sequence are divisible by 15. Is there a number n > 1 such that gcd(a(n),3)=1 or gcd(a(n),5)=1?
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EXAMPLE
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15 is in the sequence because 2*15-sigma(15)=6.
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MATHEMATICA
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Do[If[OddQ[n]&&2n-DivisorSigma[1, n]==6, Print[n]], {n, 2*10^9}]
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CROSSREFS
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Cf. A077374, A087167, A088011, A088012.
Adjacent sequences: A087482 A087483 A087484 this_sequence A087486 A087487 A087488
Sequence in context: A042725 A041096 A007541 this_sequence A069526 A061039 A063593
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KEYWORD
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hard,more,nonn
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AUTHOR
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Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Oct 23 2003
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