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Search: id:A087168
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| A087168 |
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a(n)=sum C(n+k,2k)(-2)^(n-k), k=0,..,n. |
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+0
2
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| 1, -1, -1, 7, -17, 23, -1, -89, 271, -457, 287, 967, -4049, 8279, -8641, -7193, 56143, -139657, 194399, -24569, -703889, 2209943, -3814273, 2603047, 7447951, -32756041, 68476319, -74404793, -50690897, 449691863, -1146312001
(list; graph; listen)
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OFFSET
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0,4
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FORMULA
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G.f.: (1+2x)/(4x^2+3x+1). a(n)=-3a(n-1)-4a(n-2), a(0)=1, a(1)=-1.
a(n)=(1/14)*I*sqrt(7)*[ -3/2-(1/2)*I*sqrt(7)]^n-(1/14)*I*sqrt(7)*[ -3/2+(1/2)*I *sqrt(7)]^n+(1/2)*[ -3/2+(1/2)*I*sqrt(7)]^n+(1/2)*[ -3/2-(1/2)*I*sqrt(7)]^n, with n>=0 and I=sqrt(-1) - Paolo P. Lava (ppl(AT)spl.at), Jun 12 2008
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MATHEMATICA
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CoefficientList[Series[(1 + 2x)/(4x^2 + 3x + 1), {x, 0, 30}], x]
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CROSSREFS
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Sequence in context: A144695 A125244 A070416 this_sequence A032454 A107643 A058529
Adjacent sequences: A087165 A087166 A087167 this_sequence A087169 A087170 A087171
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KEYWORD
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easy,sign
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AUTHOR
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Mario Catalani (mario.catalani(AT)unito.it), Aug 22 2003
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