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Search: id:A113179
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| A113179 |
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Expansion of 1/sqrt((1-2x)^2-8x^3). |
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+0
2
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| 1, 2, 4, 12, 40, 128, 408, 1328, 4384, 14560, 48576, 162816, 547936, 1850048, 6263680, 21257856, 72298240, 246345728, 840775424, 2873802240, 9835840512, 33704557568, 115622041600, 397032488960, 1364610270720, 4694145256448
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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In general, 1/sqrt((1-a*x)^2-4*b*x^3) expands to sum{k=0..floor(n/2), C(n-k,k)C(n-2k,k)b^k*a^(n-3k)}.
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FORMULA
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a(n)=sum{k=0..floor(n/2), C(n-k, k)C(n-2k, k)2^(n-2k)}.
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CROSSREFS
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Cf. A098479.
Sequence in context: A008404 A099214 A126946 this_sequence A056236 A028329 A025227
Adjacent sequences: A113176 A113177 A113178 this_sequence A113180 A113181 A113182
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Oct 16 2005
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