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Search: id:A098481
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| A098481 |
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Expansion of 1/sqrt((1-x)^2-12x^3). |
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+0
4
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| 1, 1, 1, 7, 19, 37, 115, 361, 937, 2599, 7777, 22195, 62701, 182647, 531829, 1534903, 4461571, 13034917, 38015899, 110994193, 325011151, 952442557, 2792471239, 8198275933, 24093817531, 70852613041, 208516575043, 614145137137
(list; graph; listen)
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OFFSET
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0,4
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COMMENT
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1/sqrt((1-x)^2-4rx^3) expands to sum{k=0..floor(n/2), binomial(n-k,k)binomial(n-2k,k)r^k}
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FORMULA
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a(n)=sum{k=0..floor(n/2), binomial(n-k, k)binomial(n-2k, k)3^k}
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CROSSREFS
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Cf. A098479, A098480.
Sequence in context: A155391 A155400 A155359 this_sequence A155334 A155422 A155370
Adjacent sequences: A098478 A098479 A098480 this_sequence A098482 A098483 A098484
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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), Sep 10 2004
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