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Search: id:A127681
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| A127681 |
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a(0) = 1. a(n+1) = sum{k=0 to n} a(n-k)*a(ceiling(k/2)). |
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2
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| 1, 1, 2, 4, 9, 19, 42, 90, 198, 428, 936, 2030, 4430, 9626, 20978, 45622, 99367, 216197, 470736, 1024420, 2230183, 4853881, 10566170, 22997974, 50061240, 108964596, 237186018, 516272178, 1123772192, 2446081048, 5324371354, 11589437278
(list; graph; listen)
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OFFSET
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0,3
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MATHEMATICA
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f[l_List] := Block[{n = Length[l] - 1}, Append[l, Sum[l[[n - k + 1]]*l[[Ceiling[k/2] + 1]], {k, 0, n}]]]; Nest[f, {1}, 32] (*Chandler*)
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CROSSREFS
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Cf. A127680.
Sequence in context: A036622 A001384 A089941 this_sequence A112569 A101463 A026776
Adjacent sequences: A127678 A127679 A127680 this_sequence A127682 A127683 A127684
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KEYWORD
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easy,nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Jan 23 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 13 2007
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