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A052958 G.f.: (1-x)/(1-3*x-2*x^3+2*x^4). 0
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; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..25.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1029

Index entries for linear recurrences with constant coefficients, signature (3,0,2,-2).

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))

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);

CROSSREFS

Sequence in context: A132353 A263900 A260696 * A247076 A177792 A193235

Adjacent sequences:  A052955 A052956 A052957 * A052959 A052960 A052961

KEYWORD

easy,nonn

AUTHOR

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

STATUS

approved

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Last modified September 22 00:25 EDT 2017. Contains 292326 sequences.