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A052740
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A simple context-free grammar in a labeled universe.
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0
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0, 1, 2, 12, 144, 2400, 50400, 1290240, 39070080, 1365154560, 54047347200, 2391175987200, 116918542540800, 6260970517401600, 364413626331955200, 22906448213096448000, 1546480919558615040000, 111605770820457897984000
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,3
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LINKS
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FORMULA
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E.g.f.: RootOf(-_Z+_Z^4+_Z^2+x)
D-finite Recurrence: {a(1)=1, a(0)=0, a(2)=2, a(3)=12, (576*n-9216*n^3-2688*n^2+192-6144*n^4)*a(n) +(-6400*n^3-23112-36480*n^2-54608*n)*a(n+1) +(13184*n+17772+896*n^2)*a(n+2) +(-14800-5176*n)*a(n+3) +1147*a(n+4) =0,.
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MAPLE
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spec := [S, {C=Prod(B, B), S=Union(B, Z, C), B=Prod(S, S)}, 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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