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Search: id:A113180
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| A113180 |
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Expansion of 1/sqrt((1-2x)^2-8x^4). |
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+0
1
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| 1, 2, 4, 8, 20, 56, 160, 448, 1240, 3440, 9632, 27200, 77216, 219840, 627200, 1793024, 5136480, 14743232, 42390400, 122064640, 351951232, 1015990528, 2936079360, 8493340672, 24591589120, 71262291456, 206666232832, 599778166784
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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^4) expands to sum{k=0..floor(n/2), C(n-2k,k)C(n-3k,k)b^k*a^(n-4k)}.
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FORMULA
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a(n)=sum{k=0..floor(n/2), C(n-2k, k)C(n-3k, k)2^(n-3k)}.
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CROSSREFS
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Cf. A098482, A113179.
Sequence in context: A000980 A123611 A082279 this_sequence A000116 A006407 A100447
Adjacent sequences: A113177 A113178 A113179 this_sequence A113181 A113182 A113183
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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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