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Search: id:A099582
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| A099582 |
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Sum C(n-k,k-1)4^(n-k-1), k=0..floor(n/2). |
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+0
3
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| 0, 0, 1, 4, 24, 112, 560, 2688, 13056, 62976, 304384, 1469440, 7096320, 34263040, 165441536, 798818304, 3857055744, 18623496192, 89922273280, 434183077888, 2096421666816, 10122418978816, 48875363631104, 235991130439680
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OFFSET
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0,4
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COMMENT
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In general a(n)=sum{k=0..floor(n/2), C(n-k,k-1)r^(n-k-1) has g.f. x^2/((1-r*x^2)(1-r*x-r*x^2)) and satisfies a(n)=r*a(n-1)+2r*a(n-2)-r^2*a(n-3)-r^2*a(n-4).
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FORMULA
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G.f.: x^2/((1-4x^2)(1-4x-4x^2)); a(n)=4a(n-1)+8a(n-2)-16a(n-3)-16a(n-4).
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CROSSREFS
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Cf. A099177, A099581.
Sequence in context: A145655 A059153 A129032 this_sequence A037132 A067312 A017976
Adjacent sequences: A099579 A099580 A099581 this_sequence A099583 A099584 A099585
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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 23 2004
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