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Search: id:A052761
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| 0, 0, 0, 0, 24, 180, 900, 3780, 14448, 52164, 181500, 615780, 2052072, 6749028, 21976500, 71007300, 228009696, 728451972, 2317445100, 7346047140, 23213772120
(list; graph; listen)
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OFFSET
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0,5
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 718
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FORMULA
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E.g.f.: exp(x)^3*x-3*exp(x)^2*x+3*x*exp(x)-x
Recurrence: {a(1)=0, a(2)=0, a(3)=0, a(4)=24, (-36*n^2-66*n-6*n^3-36)*a(n)+(11*n^3+55*n^2+66*n)*a(n+1)+(-6*n^3-24*n^2-18*n)*a(n+2)+(n^3+3*n^2+2*n)*a(n+3)}
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MAPLE
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spec := [S, {B=Set(Z, 1 <= card), S=Prod(B, B, B, Z)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A136380 A019583 A087887 this_sequence A073993 A052758 A143040
Adjacent sequences: A052758 A052759 A052760 this_sequence A052762 A052763 A052764
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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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Better description from Victor Adamchik (adamchik(AT)cs.cmu.edu), Jul 19 2001
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