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Search: id:A052960
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| A052960 |
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A simple regular expression. |
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+0
2
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| 1, 1, 3, 7, 18, 46, 118, 303, 778, 1998, 5131, 13177, 33840, 86905, 223182, 573157, 1471933, 3780093, 9707713, 24930522, 64024444, 164422126, 422254905, 1084399096, 2784861432, 7151844025, 18366756913, 47167941348, 121132691065
(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 1031
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FORMULA
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G.f.: -(-1+x+x^2)/(1-2*x-2*x^2+x^3+x^4)
Recurrence: {a(1)=1, a(0)=1, a(2)=3, a(3)=7, a(n)+a(n+1)-2*a(n+2)-2*a(n+3)+a(n+4)}
Sum(-1/331*(-25-75*_alpha+6*_alpha^2+5*_alpha^3)*_alpha^(-1-n), _alpha=RootOf(1-2*_Z-2*_Z^2+_Z^3+_Z^4))
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MAPLE
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spec := [S, {S=Sequence(Prod(Union(Sequence(Union(Prod(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: A114713 A116413 A078058 this_sequence A059512 A094297 A026107
Adjacent sequences: A052957 A052958 A052959 this_sequence A052961 A052962 A052963
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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), Feb 06 2000
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