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Search: id:A057021
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| A057021 |
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Denominator of (sum of factors of n / number of factors of n). |
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+0
7
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| 1, 2, 1, 3, 1, 1, 1, 4, 3, 2, 1, 3, 1, 1, 1, 5, 1, 2, 1, 1, 1, 1, 1, 2, 3, 2, 1, 3, 1, 1, 1, 2, 1, 2, 1, 9, 1, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1, 5, 1, 2, 1, 3, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3, 7, 1, 1, 1, 1, 1, 1
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n) = 1 when n is listed in A003601, a(n) > 1 when n is listed in A049642 - Alonso Delarte (alonso.delarte(AT)gmail.com), Jan 31 2006
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FORMULA
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a(n) =A057020(n)*A000005(n)/A000203(n) =A000005(n)/A009205(n)
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EXAMPLE
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a(12)=3 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(denom(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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Denominator[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, A057020 (numerator), A057022.
Sequence in context: A110969 A006083 A080301 this_sequence A119804 A058564 A087157
Adjacent sequences: A057018 A057019 A057020 this_sequence A057022 A057023 A057024
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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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