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A097119
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Expansion of (1-x)^2/((1-x)^3-2x^4).
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3
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1, 1, 1, 1, 3, 9, 21, 41, 75, 141, 281, 577, 1179, 2369, 4709, 9353, 18659, 37365, 74889, 149937, 299827, 599289, 1198101, 2396137, 4793051, 9587421, 19175449, 38349409, 76695403, 153388273, 306778917, 613566153, 1227140787, 2454279365
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,5
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FORMULA
| G.f. : (1-2x+x^2)/(1-3x+3x^2-x^3-2x^4); a(n)=3a(n-1)-3a(n-2)+a(n-3)+2a(n-4); a(n)=sum{k=0..floor(n/3), binomial(n-k, 3k)2^k}.
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MATHEMATICA
| CoefficientList[Series[(1-x)^2/((1-x)^3-2x^4), {x, 0, 50}], x] (* From Harvey P. Dale, Feb 25 2011 *)
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CROSSREFS
| Sequence in context: A064999 A100135 A024173 * A146608 A161214 A011843
Adjacent sequences: A097116 A097117 A097118 * A097120 A097121 A097122
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Jul 25 2004
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