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A033885
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3n - sum of divisors of n.
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4
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2, 3, 5, 5, 9, 6, 13, 9, 14, 12, 21, 8, 25, 18, 21, 17, 33, 15, 37, 18, 31, 30, 45, 12, 44, 36, 41, 28, 57, 18, 61, 33, 51, 48, 57, 17, 73, 54, 61, 30, 81, 30, 85, 48, 57, 66, 93, 20, 90, 57, 81, 58, 105, 42, 93, 48, 91, 84, 117, 12, 121, 90, 85, 65, 111, 54, 133, 78, 111, 66
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The first zero term occurs at n=120. The first negative term is a(180) = -6. For any k, k*n - sigma(n) is negative for some n. See A023199. - T. D. Noe (noe(AT)sspectra.com), Aug 07 2003
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EXAMPLE
| For n=4, 3n=12, sum of divisors of n is 1+2+4=7, so a(4)=12-7=5.
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MAPLE
| with(numtheory): for n from 1 to 150 do printf(`%d, `, 3*n-sigma(n)) od:
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CROSSREFS
| Cf. A023199.
Sequence in context: A204207 A006447 A014237 * A053079 A158901 A096736
Adjacent sequences: A033882 A033883 A033884 * A033886 A033887 A033888
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KEYWORD
| sign
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 01 2000
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