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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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1
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12, 70, 88, 1888, 4030, 5830, 32128, 521728, 1848964, 8378368, 34359083008, 66072609790, 549753192448
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 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
a(14) > 10^12. - Donovan Johnson, Dec 08 2011
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FORMULA
| Solutions to sigma[x]-2x=4
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EXAMPLE
| 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
| 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
| Cf. A045768, A045769, A088830, A059608.
Sequence in context: A101097 A067702 A163193 * A198311 A060930 A169725
Adjacent sequences: A088829 A088830 A088831 * A088833 A088834 A088835
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Oct 28 2003
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EXTENSIONS
| 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
a(13) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Dec 08 2011
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