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Search: id:A116073
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| A116073 |
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Sum of the divisors of n that are not divisible by 5. |
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+0
1
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| 1, 3, 4, 7, 1, 12, 8, 15, 13, 3, 12, 28, 14, 24, 4, 31, 18, 39, 20, 7, 32, 36, 24, 60, 1, 42, 40, 56, 30, 12, 32, 63, 48, 54, 8, 91, 38, 60, 56, 15, 42, 96, 44, 84, 13, 72, 48, 124, 57, 3, 72, 98, 54, 120, 12, 120, 80, 90, 60, 28, 62, 96, 104, 127, 14, 144, 68, 126, 96, 24
(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. 463 Entry 4(i).
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FORMULA
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a(n) is multiplicative with a(5^e) = 1, a(p^e) = (p^(e+1)-1)/(p-1) otherwise.
G.f. Sum_{k>0} k*x^k/(1-x^k) - 5kx^(5k)/(1-x^(5k)).
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PROGRAM
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(PARI) a(n) = if(n<1, 0, sumdiv(n, d, (d%5>0)*d))
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CROSSREFS
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Cf. A028887(n)=6a(n) if n>0.
Adjacent sequences: A116070 A116071 A116072 this_sequence A116074 A116075 A116076
Sequence in context: A093087 A130893 A072079 this_sequence A021292 A105828 A130880
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KEYWORD
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nonn,mult
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AUTHOR
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Michael Somos, Feb 04 2006
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