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A046520
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Sum of divisors of n - phi(n) - number of divisors of n.
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3
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-1, 0, 0, 2, 0, 6, 0, 7, 4, 10, 0, 18, 0, 14, 12, 18, 0, 27, 0, 28, 16, 22, 0, 44, 8, 26, 18, 38, 0, 56, 0, 41, 24, 34, 20, 70, 0, 38, 28, 66, 0, 76, 0, 58, 48, 46, 0, 98, 12, 67, 36, 68, 0, 94, 28, 88, 40, 58, 0, 140, 0, 62, 62, 88, 32, 116, 0, 88, 48, 112, 0, 159, 0, 74
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| Always >= 0 for n >= 2. a(n)=0 if and only if n is prime.
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REFERENCES
| D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, Section I.3.1 (but they have "tau" instead of "sigma").
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..10000
N. J. A. Sloane, My favorite integer sequences, in Sequences and their Applications (Proceedings of SETA '98).
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CROSSREFS
| Cf. A079538, A079539
a(n) = A000203(n) - A000010(n) - A000005(n).
Sequence in context: A076257 A162974 A178636 * A146076 A157195 A019781
Adjacent sequences: A046517 A046518 A046519 * A046521 A046522 A046523
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KEYWORD
| sign,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Corrected by Dean Hickerson, dean.hickerson(AT)yahoo.com, Dec 19 2006
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