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Search: id:A052919
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| A052919 |
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A simple regular expression. |
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+0
1
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| 2, 3, 7, 19, 55, 163, 487, 1459, 4375, 13123, 39367, 118099, 354295, 1062883, 3188647, 9565939, 28697815, 86093443, 258280327, 774840979, 2324522935, 6973568803, 20920706407, 62762119219, 188286357655, 564859072963
(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 902
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FORMULA
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G.f.: (2-5*x+x^2)/(-1+3*x)/(-1+x)
Recurrence: {a(1)=3, a(2)=7, a(0)=2, -3*a(n)+a(n+1)+2}
1+2*3^(n-1)
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MAPLE
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spec := [S, {S=Union(Sequence(Prod(Sequence(Z), Union(Z, Z))), Sequence(Z))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A122724 A033844 A037028 this_sequence A005807 A060276 A025563
Adjacent sequences: A052916 A052917 A052918 this_sequence A052920 A052921 A052922
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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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