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Search: id:A052937
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| A052937 |
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A simple regular expression. |
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+0
2
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| 2, 3, 6, 13, 30, 71, 170, 409, 986, 2379, 5742, 13861, 33462, 80783, 195026, 470833, 1136690, 2744211, 6625110, 15994429, 38613966, 93222359, 225058682, 543339721, 1311738122, 3166815963, 7645370046, 18457556053, 44560482150
(list; graph; listen)
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OFFSET
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0,1
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 928
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FORMULA
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G.f.: -(-2+3*x+x^2)/(-1+x)/(-1+2*x+x^2)
Recurrence: {a(2)=6, a(1)=3, a(0)=2, -a(n)-2*a(n+1)+a(n+2)+2}
1+Sum(1/4*(1+_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+2*_Z+_Z^2))
a(n) = A000129(n+1)+1, where A000129 are the Pell Numbers. - Graeme McRae (g_m(AT)mcraefamily.com), Aug 03 2006
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MAPLE
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spec := [S, {S=Union(Sequence(Z), Sequence(Union(Z, Z, Prod(Z, Z))))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
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CROSSREFS
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Cf. A001333.
Sequence in context: A107316 A124682 A079512 this_sequence A005554 A077212 A076836
Adjacent sequences: A052934 A052935 A052936 this_sequence A052938 A052939 A052940
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 05 2000
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