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A133669
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a(n)=a(n-1)-49*a(n-2), a(0)=1, a(1)=7 .
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1
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1, 7, -42, -385, 1673, 20538, -61439, -1067801, 1942710, 54264959, -40927831, -2699910822, -694447103, 131601183175, 165629091222, -6282828884353, -14398654354231
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| G.f.:(1+6*x)/(1-x+49*x^2) .
a(n)=Sum_{k, 0<=k<=n}A133607(n,k)*7^k. - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Dec 30 2007
a(n)=(1/30)*I*[1/2-(1/2)*I*sqrt(195)]^n*sqrt(195)+(1/2)*[1/2-(1/2)*I*sqrt(195)]^n+(1/2) *[1/2+(1/2)*I*sqrt(195)]^n-(1/30)*I*[1/2+(1/2)*I*sqrt(195)]^n*sqrt(195), with n>=0 and I=sqrt(-1) [From Paolo P. Lava (paoloplava(AT)gmail.com), Aug 28 2008]
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CROSSREFS
| Sequence in context: A025593 A048862 A174224 * A205340 A202862 A043064
Adjacent sequences: A133666 A133667 A133668 * A133670 A133671 A133672
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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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