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Search: id:A112290
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| A112290 |
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Numerator of sum{k=1 to n} 1/S(n,k), where S(n,k) is a Stirling number of the second kind. |
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+0
2
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| 1, 2, 7, 97, 331, 77089, 562609, 19352053463, 6781959158383, 4060488497950626661, 2877117441205884350399, 7936150834464388482084637351, 21924183158935156780838459
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OFFSET
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1,2
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EXAMPLE
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a(4) = 97, the numerator of 1/1 + 1/7 + 1/6 + 1 = 97/42.
The first few fractions are: 1, 2, 7/3, 97/42, 331/150, 77089/36270, 562609/270900,
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MAPLE
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with(combinat): a:=n->numer(sum(1/stirling2(n, k), k=1..n)): seq(a(n), n=1..15); (Deutsch)
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MATHEMATICA
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f[n_] := Sum[1/StirlingS2[n, k], {k, n}]; Table[Numerator[f[n]], {n, 15}] (*Chandler*)
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CROSSREFS
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Cf. A112291.
Sequence in context: A123995 A056161 A076740 this_sequence A072059 A087589 A002812
Adjacent sequences: A112287 A112288 A112289 this_sequence A112291 A112292 A112293
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KEYWORD
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nonn,frac
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Sep 01 2005
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EXTENSIONS
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Extended by Emeric Deutsch (deutsch(AT)duke.poly.edu) and Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 02 2005
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