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Search: id:A088832
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| A088832 |
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Numbers n whose abundance sigma[n]-2n=+4. A subset of A045769. |
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+0
2
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| 12, 70, 88, 1888, 4030, 5830, 32128, 521728, 1848964, 8378368, 34359083008, 66072609790
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If 2^m-5 is prime then n=2^(m-1)*(2^m-5) is in the sequence (see comment lines of the sequence A088831). 12, 88, 1888, 32128, 521728, 8378368 & 34359083008 are such terms. - OFarideh Firoozbakht (mymontain(AT)yahoo.com), Feb 15 2008
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FORMULA
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Solutions to sigma[x]-2x=4
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EXAMPLE
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Abundances of terms in A045769: {-5,4,4,4,4,4,4,4,4,4} so A045769[1]=9 is not here.
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MATHEMATICA
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Do[If[DivisorSigma[1, n]==2n+4, Print[n]], {n, 650000000}] - OFarideh Firoozbakht (mymontain(AT)yahoo.com), Feb 15 2008
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CROSSREFS
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Cf. A045768, A045769, A088830.
Cf. A059608.
Sequence in context: A101097 A067702 A163193 this_sequence A060930 A101523 A143698
Adjacent sequences: A088829 A088830 A088831 this_sequence A088833 A088834 A088835
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Oct 28 2003
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EXTENSIONS
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One more terms from Farideh Firoozbakht (mymontain(AT)yahoo.com), Feb 15 2008
a(11)-a(12) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Dec 23 2008
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