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A052997
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Expansion of (1+x-x^3)/((1-2x)(1-x^2)).
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1
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1, 3, 7, 14, 29, 58, 117, 234, 469, 938, 1877, 3754, 7509, 15018, 30037, 60074, 120149, 240298, 480597, 961194, 1922389, 3844778, 7689557, 15379114, 30758229, 61516458, 123032917, 246065834, 492131669, 984263338, 1968526677
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1075
Index to sequences with linear recurrences with constant coefficients, signature (2,1,-2).
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FORMULA
| G.f.: -(-x+x^3-1)/(-1+x^2)/(-1+2*x)
Recurrence: {a(0)=1, -2*a(n)-a(n+1)+a(n+2)-1, a(1)= 3, a(2)=7, a(3)=14}
11/6*2^n+Sum(-1/6*(2+_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+_Z^2))
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MAPLE
| spec := [S, {S=Prod(Union(Sequence(Prod(Z, Z)), Z), Sequence(Union(Z, Z)))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A192065 A157672 A125899 * A074988 A066225 A139817
Adjacent sequences: A052994 A052995 A052996 * A052998 A052999 A053000
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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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