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A052958
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G.f.: (1-x)/(1-3*x-2*x^3+2*x^4).
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0
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1, 2, 6, 20, 62, 194, 610, 1914, 6006, 18850, 59158, 185658, 582662, 1828602, 5738806, 18010426, 56523158, 177389882, 556712886, 1747164122, 5483225814, 17208323450, 54005872822, 169489741850, 531919420822, 1669353361210
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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LINKS
| Index entries for sequences related to linear recurrences with constant coefficients, (3,0,2,-2).
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1029
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FORMULA
| Recurrence: {a(0)=1, a(1)=2, a(2)=6, a(3)=20, 2*a(n)-2*a(n+1)-3*a(n+3)+a(n+4)=0}
Sum(-1/3259*(-491-503*_alpha-272*_alpha^2+498*_alpha^3)*_alpha^(-1-n), _alpha=RootOf(1-3*_Z-2*_Z^3+2*_Z^4))
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MAPLE
| spec := [S, {S=Sequence(Prod(Union(Prod(Z, Z), Sequence(Z)), Union(Z, Z)))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A136883 A057766 A132353 * A177792 A193235 A199102
Adjacent sequences: A052955 A052956 A052957 * A052959 A052960 A052961
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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EXTENSIONS
| More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 06 2000
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