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Search: id:A112291
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| A112291 |
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Denominator 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, 1, 3, 42, 150, 36270, 270900, 9440379900, 3332912051700, 2004302168707167000, 1424191116445997823000, 3936008766237071969447818200, 10888542544398564939894000, 3606055788316324023953497288103040
(list; graph; listen)
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OFFSET
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1,3
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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a(4) = 42, the denominator 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->denom(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[Denominator[f[n]], {n, 15}] (*Chandler*)
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CROSSREFS
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Cf. A112290.
Sequence in context: A055755 A116006 A079826 this_sequence A063040 A015786 A157537
Adjacent sequences: A112288 A112289 A112290 this_sequence A112292 A112293 A112294
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KEYWORD
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nonn,frac
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AUTHOR
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Leroy Quet 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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