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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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48
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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, 39, 48, 63, 18, 89
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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REFERENCES
| M. Lal and A. Forbes, A note on Chowla's function, Math. Comp., 25 (1971), 923-925.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..10000
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FORMULA
| a(n) = A000203(n) - A065475(n).
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EXAMPLE
| Divisors of 20 are 1,2,4,5,10,20, so a(20)=2+4+5+10=21.
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MAPLE
| A048050 := proc(n) if n > 1 then numtheory[sigma](n)-1-n ; else 0; end if; end proc:
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MATHEMATICA
| f[n_]:=Plus@@Divisors[n]-n-1; Table[f[n], {n, 100}] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Sep 13 2009]
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PROG
| (MAGMA) A048050:=func< n | n eq 1 or IsPrime(n) select 0 else &+[ a: a in Divisors(n) | a ne 1 and a ne n ] >; [ A048050(n): n in [1..100] ]; // Klaus Brockhaus, Mar 04 2011
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CROSSREFS
| Cf. A001065, A000593, A002954, A048995.
Cf. A007956, A048671, A182936.
Sequence in context: A086131 A104755 A054013 * A078153 A104035 A196409
Adjacent sequences: A048047 A048048 A048049 * A048051 A048052 A048053
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KEYWORD
| nonn,nice,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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