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Search: id:A052950
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| A052950 |
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A simple regular expression. |
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+0
2
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| 2, 1, 3, 4, 9, 16, 33, 64, 129, 256, 513, 1024, 2049, 4096, 8193, 16384, 32769, 65536, 131073, 262144, 524289, 1048576, 2097153, 4194304, 8388609, 16777216, 33554433, 67108864, 134217729, 268435456, 536870913, 1073741824, 2147483649
(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 1009
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FORMULA
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G.f.: (x^3-x^2-3*x+2)/(-1+2*x)/(-1+x^2)
Recurrence: {a(1)=1, a(3)=4, a(2)=3, a(0)=2, -2*a(n)-a(n+1)+a(n+2)+1}
2^(n-1)+Sum(1/2*_alpha^(-n), _alpha=RootOf(-1+_Z^2))
E.g.f. : cosh(x)(1+exp(x)); a(n)=(2^n+1+(-1)^n+0^n)/2. - Paul Barry (pbarry(AT)wit.ie), Sep 18 2003
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MAPLE
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spec := [S, {S=Union(Sequence(Prod(Sequence(Z), Z)), Sequence(Prod(Z, Z)))}, unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A134876 A019612 A007444 this_sequence A086851 A001054 A099866
Adjacent sequences: A052947 A052948 A052949 this_sequence A052951 A052952 A052953
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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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