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Search: id:A052912
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| A052912 |
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A simple regular expression. |
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+0
3
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| 1, 2, 4, 10, 24, 56, 132, 312, 736, 1736, 4096, 9664, 22800, 53792, 126912, 299424, 706432, 1666688, 3932224, 9277312, 21888000, 51640448, 121835520, 287447040, 678174976, 1600020992, 3774936064, 8906222080, 21012486144, 49574844416
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 892
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FORMULA
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G.f.: -1/(-1+2*x^3+2*x)
Recurrence: {a(0)=1, a(2)=4, a(1)=2, 2*a(n)+2*a(n+2)-a(n+3)}
Sum(1/43*(8+12*_alpha^2+9*_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+2*_Z^3+2*_Z))
a(n)=sum{k=0..n, C(k, floor((n-k)/2))2^k(1+(-1)^(n-k))/2}; - Paul Barry (pbarry(AT)wit.ie), Jan 12 2006
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MAPLE
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spec := [S, {S=Sequence(Union(Prod(Union(Z, Z), Z, Z), Z, Z))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A095214 A002525 A159328 this_sequence A024740 A025275 A165409
Adjacent sequences: A052909 A052910 A052911 this_sequence A052913 A052914 A052915
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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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