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A077374
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Odd numbers whose abundance b satisfies -10 <= b <= 10, where the abundance of a number n is A(n) = sigma(n) - 2n.
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22
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1, 3, 5, 7, 9, 11, 15, 21, 315, 1155, 8925, 32445, 442365, 815634435
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OFFSET
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1,2
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COMMENTS
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Apart from {1, 3, 5, 7, 9, 11, 15, 21, 315}, subset of A088012. Probably finite. - Charles R Greathouse IV, Mar 28 2011
The abundance of the given terms a(1..14) is: (-1, -2, -4, -6, -5, -10, -6, -10, -6, -6, 6, 6, 6, -6). See also A171929, A188263 and A188597 for numbers with abundancy sigma(n)/n close to 2. - M. F. Hasler, Feb 21 2017
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LINKS
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Eric Weisstein's World of Mathematics, Abundance
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EXAMPLE
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sigma(32445) = 64896 and 32445*2 = 64890, which makes the odd number 32445 six away from perfection: A(32445) = 6 and hence in this sequence.
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MATHEMATICA
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Select[Range[1, 10^6, 2], -10 <= DivisorSigma[1, #] - 2 # <= 10 &] (* Michael De Vlieger, Feb 22 2017 *)
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PROG
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(PARI) forstep(n=1, 442365, 2, if(abs(sigma(n)-2*n)<=10, print1(n, ", ")))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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