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Search: id:A112447
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| 1, 1, 3, 1, 5, 3, 11, 5, 21, 11, 43, 21, 85, 43, 171, 85, 341, 171, 683, 341, 1365, 683, 2731, 1365, 5461, 2731, 10923, 5461, 21845, 10923, 43691, 21845, 87381, 43691, 174763, 87381, 349525, 174763, 699051, 349525, 1398101, 699051, 2796203
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Consider the Harmonacci sequence: H(1)=x, H(2)=y, H(3)=2xy/(x+y), H(4)=4xy/(3x+y)...; H(m) is the harmonic mean of H(m-1) and H(m-2). a(2n) and a(2n+1) are the denominator coefficients of H(n+3).
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FORMULA
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a(n) = (a(n-1)+1)/2 for n=2, 6, 10...
a(n) = 4*a(n-1)-1 for n=3, 7, 11...
a(n) = (a(n-1)-1)/2 for n=4, 8, 12...
a(n) = 4*a(n-1)+1 for n=5, 9, 13....
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CROSSREFS
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Cf. A001045.
Sequence in context: A129095 A105604 A117576 this_sequence A002323 A117853 A104734
Adjacent sequences: A112444 A112445 A112446 this_sequence A112448 A112449 A112450
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KEYWORD
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nonn
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AUTHOR
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Edwin F. Sampang (efs_files(AT)yahoo.com), Dec 12 2005
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EXTENSIONS
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Edited by Don Reble (djr(AT)nk.ca), Jan 25 2006
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