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Search: id:A057020
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| A057020 |
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Numerator of (sum of factors of n / number of factors of n). |
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+0
3
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| 1, 3, 2, 7, 3, 3, 4, 15, 13, 9, 6, 14, 7, 6, 6, 31, 9, 13, 10, 7, 8, 9, 12, 15, 31, 21, 10, 28, 15, 9, 16, 21, 12, 27, 12, 91, 19, 15, 14, 45, 21, 12, 22, 14, 13, 18, 24, 62, 19, 31, 18, 49, 27, 15, 18, 15, 20, 45, 30, 14, 31, 24, 52, 127, 21, 18, 34, 21, 24, 18
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n) =A057021(n)*A000203(n)/A000005(n) =A000203(n)/A009205(n) =(A057022(n)+A054025(n)/A000005(n))*A057021(n)
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EXAMPLE
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a(12)=14 since the 6 factors of 12 are 1, 2, 3, 4, 6 and 12 and 1+2+3+4+6+12=28 and 28/6=14/3
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MAPLE
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with(numtheory): seq(numer(sigma(n)/tau(n)), n=1..70) ; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 04 2008
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MATHEMATICA
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Numerator[Table[(Plus @@ Divisors[n])/Length[Divisors[n]], {n, 70}]] (Alonso Delarte (alonso.delarte(AT)gmail.com))
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CROSSREFS
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Cf. A000005, A000203, A009205, A054025, A057021 (denominator), A057022.
Adjacent sequences: A057017 A057018 A057019 this_sequence A057021 A057022 A057023
Sequence in context: A137822 A099378 A071190 this_sequence A165794 A075270 A067872
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KEYWORD
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frac,nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Jul 21 2000
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