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Search: id:A090634
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| A090634 |
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Start with the sequence [1, 1/2, 1/3, ..., 1/n]; form new sequence of n-1 terms by taking averages of successive terms; repeat until reach a single number F(n); a(n) = denominator of F(n). |
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3
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| 1, 4, 12, 32, 80, 64, 448, 1024, 2304, 5120, 11264, 8192, 53248, 114688, 245760, 524288, 1114112, 262144, 4980736, 2097152, 3145728, 46137344, 96468992, 67108864, 419430400, 872415232, 1811939328, 3758096384, 7784628224, 5368709120, 33285996544, 68719476736
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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Putnam Competition, 2003, Problem B2.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..200
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FORMULA
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a(n)=A131135(n)/2. - Paul Barry (pbarry(AT)wit.ie), Jun 17 2007
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EXAMPLE
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n=3: [1, 1/2, 1/3] -> [3/4, 5/6] -> [7/12], so F(3) = 7/12. Sequence of F(n)'s begins 1, 3/4, 7/12, 15/32, 31/80, 21/64, 127/448, 255/1024, ...
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CROSSREFS
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Cf. A090633.
Sequence in context: A107035 A118885 A097392 this_sequence A085750 A097067 A139756
Adjacent sequences: A090631 A090632 A090633 this_sequence A090635 A090636 A090637
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KEYWORD
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nonn,frac
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AUTHOR
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njas, Dec 13 2003
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