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Search: id:A052550
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| A052550 |
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A simple regular expression. |
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+0
4
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| 1, 1, 4, 11, 35, 108, 337, 1049, 3268, 10179, 31707, 98764, 307641, 958273, 2984932, 9297787, 28961747, 90213164, 281005665, 875306665, 2726499332, 8492793331, 26454265995, 82402592652, 256676457289, 799523432529, 2490441569572
(list; graph; listen)
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OFFSET
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0,3
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 487
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FORMULA
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G.f.: -(-1+2*x)/(1-3*x-x^2+2*x^3)
Recurrence: {a(1)=1, a(0)=1, a(2)=4, 2*a(n)-a(n+1)-3*a(n+2)+a(n+3)}
Sum(-1/229*(-5-74*_alpha+16*_alpha^2)*_alpha^(-1-n), _alpha=RootOf(1-3*_Z-_Z^2+2*_Z^3))
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MAPLE
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spec := [S, {S=Sequence(Prod(Z, Union(Z, Sequence(Union(Z, Z)))))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A119716 A000626 A036364 this_sequence A114248 A054577 A106640
Adjacent sequences: A052547 A052548 A052549 this_sequence A052551 A052552 A052553
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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 06 2000
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