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A088832
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Numbers n whose abundance is 4: sigma(n) - 2n = 4.
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8
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12, 70, 88, 1888, 4030, 5830, 32128, 521728, 1848964, 8378368, 34359083008, 66072609790, 549753192448, 259708613909470, 2251799645913088
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OFFSET
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1,1
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COMMENTS
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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. - Farideh Firoozbakht, Feb 15 2008
Any term x of this sequence can be combined with any term y of A125246 to satisfy the property (sigma(x)+sigma(y))/(x+y) = 2, which is a necessary (but not sufficient) condition for two numbers to be amicable. - Timothy L. Tiffin, Sep 13 2016
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LINKS
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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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PROG
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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