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A110513
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Expansion of (1+x)/(1+2x+x^3).
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4
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1, -1, 2, -5, 11, -24, 53, -117, 258, -569, 1255, -2768, 6105, -13465, 29698, -65501, 144467, -318632, 702765, -1549997, 3418626, -7540017, 16630031, -36678688, 80897393, -178424817, 393528322, -867954037, 1914332891, -4222194104, 9312342245, -20539017381, 45300228866, -99912799977
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OFFSET
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0,3
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COMMENTS
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Diagonal sums of A110511.
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LINKS
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Harvey P. Dale, Table of n, a(n) for n = 0..1000
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FORMULA
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a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, (-1)^(n-k-j)*C(n-k, j)*(-2)^(j-k)*C(k, j-k)}}
a(0)=1, a(1)=-1, a(2)=2, a(n)=-2*a(n-1)-a(n-3) From Harvey P. Dale, Jun 27 2012
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MATHEMATICA
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CoefficientList[Series[(1+x)/(1+2x+x^3), {x, 0, 40}], x] (* or *) LinearRecurrence[ {-2, 0, -1}, {1, -1, 2}, 40] (* Harvey P. Dale, Jun 27 2012 *)
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CROSSREFS
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A minor variation of A052980.
Sequence in context: A077864 A052980 A190512 * A018115 A018007 A071879
Adjacent sequences: A110510 A110511 A110512 * A110514 A110515 A110516
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KEYWORD
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easy,sign
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AUTHOR
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Paul Barry, Jul 24 2005
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STATUS
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approved
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