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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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1
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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; refs; listen; history; internal format)
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OFFSET
| 1,4
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EXAMPLE
| {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
| 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
| Cf. A127939.
Sequence in context: A006545 A121050 A089402 * A006796 A006076 A086628
Adjacent sequences: A127937 A127938 A127939 * A127941 A127942 A127943
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KEYWORD
| frac,nonn
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AUTHOR
| Leroy Quet Feb 08 2007
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EXTENSIONS
| Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 09 2007
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