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A109220
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Expansion of (1+x-x^2)/(1-2x-2x^2+x^4).
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0
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1, 3, 7, 20, 53, 143, 385, 1036, 2789, 7507, 20207, 54392, 146409, 394095, 1060801, 2855400, 7685993, 20688691, 55688567, 149899116, 403489373, 1086088287, 2923466753, 7869210964, 21181866061, 57016065763, 153472396895
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OFFSET
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0,2
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COMMENTS
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Transform of 2^n under matrix A108756.
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LINKS
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FORMULA
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a(n)=2a(n-1)+2a(n-2)-a(n-4); a(n)=a(n)=sum{k=0..n, binomial(floor((n+k+1)/2)+k, floor((n+k)/2)-k)*2^k}.
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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