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Search: id:A127940
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| A127940 |
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a(n) = denominator of b(n), where b(1)=1, b(n+1) = sum{k|n} 1/b(k). |
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+0
2
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| 1, 1, 1, 2, 3, 8, 22, 71, 93, 638, 9144, 26821, 2373690, 11013191, 950468551, 23819080360, 4860600739719, 18887557655957, 23748158395676, 102452785866447, 1153981434332852712, 722919835385951370578
(list; graph; listen)
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OFFSET
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1,4
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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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{b(n)}:1,1,2,3/2,8/3,11/8,71/22,93/71,...So b(7) = sum{k|6} 1/b(k) = 1/b(1) + 1/ b(2) + 1/b(3) + 1/b(6) = 1 + 1 + 1/2 + 8/11 = 71/22.
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MATHEMATICA
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f[l_List] := Block[{n = Length[l], d = Divisors[n]}, Append[l, Sum[1/l[[d[[i]]]], {i, Length[d]}]]]; Denominator[Nest[f, {1}, 22]] (*Chandler*)
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CROSSREFS
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Cf. A127939.
Adjacent sequences: A127937 A127938 A127939 this_sequence A127941 A127942 A127943
Sequence in context: A006545 A121050 A089402 this_sequence A006796 A006076 A086628
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KEYWORD
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frac,nonn
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AUTHOR
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Leroy Quet Feb 08 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 09 2007
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