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A133665
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a(n)=a(n-1)-9*a(n-2), a(0)=1, a(1)=3 .
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1
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1, 3, -6, -33, 21, 318, 129, -2733, -3894, 20703, 55749, -130578, -632319, 542883, 6233754, 1347807, -54755979, -66886242, 425917569, 1027093747, -2805364374, -120564080097, 13191871269, 121699544142, 2972702721, -1092323194557
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| G.f.:(1+2*x)/(1-x+9*x^2).
a(n)=Sum_{k, 0<=k<=n}A133607(n,k)*3^k. - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Dec 29 2007
a(n)=-(1/14)*I*sqrt(35)*[(1/2)+(1/2)*I*sqrt(35)]^n+(1/14)*I*sqrt(35)*[(1/2)-(1/2)*I *sqrt(35)]^n+(1/2)*[(1/2)+(1/2)*I*sqrt(35)]^n+(1/2)*[(1/2)-(1/2)*I*sqrt(35)]^n, with n>=0 and I=sqrt(-1) [From Paolo P. Lava (paoloplava(AT)gmail.com), Nov 18 2008]
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CROSSREFS
| Sequence in context: A103091 A186940 A101751 * A124178 A192166 A101142
Adjacent sequences: A133662 A133663 A133664 * A133666 A133667 A133668
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KEYWORD
| easy,sign
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AUTHOR
| Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Dec 28 2007
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