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Search: id:A087171
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| A087171 |
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a(n)=sum C(n+k,2k)(-5)^(n-k), k=0,..,n. |
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+0
1
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| 1, -4, 11, 1, -284, 2531, -15679, 77836, -308549, 831041, 234356, -22885229, 200108161, -1228842724, 6056880491, -23790856319, 62695694596, 30510156611, -1841983774399, 15815100054316, -96286306128869, 471199253801921, -1833635630995564, 4722739333912051
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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G.f.: (1+5x)/(25x^2+9x+1). a(n)=-9a(n-1)-25a(n-2), a(0)=1, a(1)=-4.
a(n)=(1/2)*[ -9/2+(1/2)*I*sqrt(19)]^n+(1/2)*[ -9/2-(1/2)*I*sqrt(19)]^n+(1/38)*I*sqrt(19)*[ -9/2-(1/2)*I*sqrt(19)]^n-(1/38)*I*sqrt(19)*[ -9/2+(1/2)*I*sqrt(19)]^n, with n>=0 and I=sqrt(-1) - Paolo P. Lava (ppl(AT)spl.at), Jun 16 2008
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MATHEMATICA
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CoefficientList[Series[(1 + 5x)/(25x^2 + 9x + 1), {x, 0, 25}], x]
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CROSSREFS
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Sequence in context: A132150 A091389 A113249 this_sequence A066333 A115642 A115643
Adjacent sequences: A087168 A087169 A087170 this_sequence A087172 A087173 A087174
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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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