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Search: id:A113957
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| A113957 |
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Sum of the divisors of n which are not divisible by 7. |
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+0
1
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| 1, 3, 4, 7, 6, 12, 1, 15, 13, 18, 12, 28, 14, 3, 24, 31, 18, 39, 20, 42, 4, 36, 24, 60, 31, 42, 40, 7, 30, 72, 32, 63, 48, 54, 6, 91, 38, 60, 56, 90, 42, 12, 44, 84, 78, 72, 48, 124, 1, 93, 72, 98, 54, 120, 72, 15, 80, 90, 60, 168, 62, 96, 13, 127, 84, 144, 68, 126, 96, 18, 72
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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B. C. Berndt, Ramanujan's Notebooks Part III, Springer-Verlag, see p. 467, Entry 5(i).
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FORMULA
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a(n) is multiplicative and a(p^e) = 1, if p=7, a(p^e) = (p^(e+1)-1)/(p-1) otherwise.
G.f.: ((theta_3(z)*theta_3(7z) + theta_2(z)*theta_2(7z))^2-1)/4.
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PROGRAM
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(PARI) a(n)=if(n<1, 0, sigma(n/7^valuation(n, 7)))
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CROSSREFS
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Cf. A028594(n)=4*a(n) if n>0.
Sequence in context: A087030 A126253 A057032 this_sequence A073185 A073183 A049418
Adjacent sequences: A113954 A113955 A113956 this_sequence A113958 A113959 A113960
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KEYWORD
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nonn,mult
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AUTHOR
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Michael Somos, Nov 10 2005
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