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Search: id:A048050
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| A048050 |
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Chowla's function: sum of divisors of n except 1 and n. |
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+0
40
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| 0, 0, 0, 2, 0, 5, 0, 6, 3, 7, 0, 15, 0, 9, 8, 14, 0, 20, 0, 21, 10, 13, 0, 35, 5, 15, 12, 27, 0, 41, 0, 30, 14, 19, 12, 54, 0, 21, 16, 49, 0, 53, 0, 39, 32, 25, 0, 75, 7, 42, 20, 45, 0, 65, 16, 63, 22, 31, 0, 107, 0, 33, 40, 62, 18, 77, 0, 57, 26, 73, 0, 122, 0
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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In other words, the sum of the nontrivial divisors of n [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Aug 10 2009.
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REFERENCES
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M. Lal and A. Forbes, A note on Chowla's function, Math. Comp., 25 (1971), 923-925.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
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EXAMPLE
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Divisors of 20 are 1,2,4,5,10,20, so a(20)=2+4+5+10=21.
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MAPLE
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with(numtheory); n->sigma(n)-n-1; # n>1
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MATHEMATICA
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f[n_]:=Plus@@Divisors[n]-n-1; lst={}; Do[AppendTo[lst, f[n]], {n, 6!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Sep 13 2009]
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CROSSREFS
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Cf. A001065, A000593, A002954, A048995.
Sequence in context: A086131 A104755 A054013 this_sequence A078153 A104035 A115333
Adjacent sequences: A048047 A048048 A048049 this_sequence A048051 A048052 A048053
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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