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A052725
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A simple context-free grammar in a labeled universe.
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0
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0, 0, 0, 0, 24, 480, 10080, 262080, 8104320, 287400960, 11496038400, 512691379200, 25231888281600, 1358412133478400, 79419074570035200, 5011102330730496000, 339416862385176576000, 24564200609223475200000
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,5
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LINKS
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FORMULA
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E.g.f.: RootOf(-_Z+_Z^4+_Z^2+x)-RootOf(-_Z+_Z^4+_Z^2+x)^2-x
D-finite Recurrence: {a(1)=0, a(2)=0, a(3)=0, a(4)=24, a(5)=480, a(6)=10080, (-32256*n^3+85248*n^2-73728*n^5+2304*n-4608-184320*n^4)*a(n) +(-41472*n^3-241344*n^2-92736-289440*n+9216*n^4)*a(n+1) +(-59520*n^2-34048*n^3+79800+56512*n)*a(n+2) +(-7456*n^2-46176*n-61988)*a(n+3) +(-572+2228*n)*a(n+4) +217*a(n+5) =0.
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MAPLE
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spec := [S, {B=Prod(C, C), C=Union(B, S, Z), S=Prod(B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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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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STATUS
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approved
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