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A087690
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Denominators of successive partial sums of sum(1/(2^n-1)).
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1
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1, 3, 21, 35, 1085, 9765, 1240155, 21082635, 1539032355, 16929355905, 34654391537535, 150169029995985, 1230034524697113135, 17630494853991954935, 2662204722952785195185, 410511968279319477097527
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Least common denominators of A000225.
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FORMULA
| a(n) = lcm(a(n-1), 2^n-1)
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EXAMPLE
| a(4)=35 because 1/1 + 1/3 + 1/7 + 1/15 = 54/35.
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MATHEMATICA
| f[n_] := Denominator[Sum[1/(2^i - 1), {i, n}]]; Array[f, 16] (* Robert G. Wilson v, May 25 2011 *)
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CROSSREFS
| Cf. A000225, A087689.
Sequence in context: A089323 A100986 A075732 * A191763 A076169 A178082
Adjacent sequences: A087687 A087688 A087689 * A087691 A087692 A087693
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KEYWORD
| frac,nonn
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AUTHOR
| Keenan Pepper (keenanpepper(AT)gmail.com), Sep 27 2003
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EXTENSIONS
| More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Oct 26 2003
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