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A133631
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a(n)=a(n-1)-4*a(n-2), a(0)=1, a(1)=2 .
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1
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1, 2, -2, -10, -2, 38, 46, -106, -290, 134, 1294, 758, -4418, -7450, 10222, 40022, -866, -160954, -157490, 486326, 1116286, -829018, -5294162, -1978090, 19198558, 27110918, -49683314, -158126986, 40606270, 673114214, 510689134, -2181767722, -4224524258
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| G.f.:(1+x)/(1-x+4*x^2) .
a(n)=Sum_{k, 0<=k<=n}A133607(n,k)*2^k. - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Dec 29 2007
a(n)=(1/10)*I*sqrt(15)*[(1/2)-(1/2)*I*sqrt(15)]^n-(1/10)*I*sqrt(15)*[(1/2)+(1/2)*I *sqrt(15)]^n+(1/2)*[(1/2)-(1/2)*I*sqrt(15)]^n+(1/2)*[(1/2)+(1/2)*I*sqrt(15)]^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: A135816 A157341 A038036 * A137450 A163937 A083457
Adjacent sequences: A133628 A133629 A133630 * A133632 A133633 A133634
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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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