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Search: id:A052776
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| 0, 0, 0, 0, 0, 120, 1440, 10920, 67200, 367416, 1864800, 9003720, 41976000, 190788312, 850930080, 3741028200, 16264684800, 70093951608, 299953709280, 1276255985160, 5404640136000
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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 733
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FORMULA
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G.f.: x*exp(x)^4-4*exp(x)^3*x+6*exp(x)^2*x-4*x*exp(x)+x
Recurrence: {a(1)=0, a(2)=0, a(4)=0, a(3)=0, (1200*n+840*n^2+240*n^3+576+24*n^4)*a(n)+(-1200*n-1300*n^2-450*n^3-50*n^4)*a(n+1)+(35*n^4+420*n+665*n^2+280*n^3)*a(n+2)+(-80*n-10*n^4-140*n^2-70*n^3)*a(n+3)+(n^4+6*n^3+11*n^2+6*n)*a(n+4), a(5)=120}
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MAPLE
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spec := [S, {B=Set(Z, 1 <= card), S=Prod(Z, B, B, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A052777 A052765 A167549 this_sequence A052770 A027795 A053567
Adjacent sequences: A052773 A052774 A052775 this_sequence A052777 A052778 A052779
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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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