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A052874
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A simple grammar.
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0
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0, 0, 2, 15, 112, 925, 8556, 88249, 1007056, 12612681, 172092340, 2541367741, 40385290584, 687120886621, 12461362029676, 239945693311185, 4888311943969696, 105038684764873489, 2373935421890157156
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listen;
history;
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internal format)
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OFFSET
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0,3
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LINKS
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Table of n, a(n) for n=0..18.
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 845
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FORMULA
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E.g.f.: -x/(-1+x)*(exp(-x/(-1+x))-1)
Recurrence: {a(1)=0, a(0)=0, a(2)=2, (-n^4-6*n^3-11*n^2-6*n)*a(n)+(3*n^3+18*n^2+33*n+18)*a(n+1)+(-3*n^2-14*n-15)*a(n+2)+(n+2)*a(n+3)}
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MAPLE
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spec := [S, {C=Sequence(Z, 1 <= card), B=Set(C, 1 <= card), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A140637 A022026 A026113 * A074622 A031507 A207998
Adjacent sequences: A052871 A052872 A052873 * A052875 A052876 A052877
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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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