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Search: id:A052710
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| A052710 |
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A simple context-free grammar. |
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+0
1
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| 0, 0, 0, 0, 1, 4, 14, 52, 201, 792, 3168, 12844, 52676, 218148, 910996, 3832072, 16222352, 69061200, 295477550, 1269863304, 5479456290
(list; graph; listen)
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OFFSET
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0,6
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 665
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FORMULA
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G.f.: RootOf(-_Z+_Z^4+_Z^2+x)-RootOf(-_Z+_Z^4+_Z^2+x)^2-x
Recurrence: {a(1)=0, a(2)=0, a(4)=1, a(3)=0, a(5)=4, a(6)=14, (2304-4608*n-36864*n^2+73728*n^3)*a(n)+(46368+121536*n+59904*n^2-9216*n^3)*a(n+1)+(-79800-56512*n+59520*n^2+34048*n^3)*a(n+2)+(200516*n+185964+68544*n^2+7456*n^3)*a(n+3)+(-15024*n^2-22732*n+6864-2228*n^3)*a(n+4)+(-217*n^3-2604*n^2-10199*n-13020)*a(n+5)}
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MAPLE
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spec := [S, {C=Prod(B, B), S=Prod(C, C), B=Union(S, C, Z)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A099486 A047033 A017947 this_sequence A129997 A125783 A090319
Adjacent sequences: A052707 A052708 A052709 this_sequence A052711 A052712 A052713
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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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