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Search: id:A052840
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| 0, 0, 2, 9, 56, 450, 4464, 52920, 731520, 11566800, 206035200, 4083488640, 89137843200, 2124970848000, 54929029478400, 1530259226496000, 45705137084006400, 1456873475016960000, 49362677881380864000
(list; graph; listen)
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OFFSET
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0,3
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 807
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FORMULA
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E.g.f.: ln((-1+x)/(-1+2*x))*x
Recurrence: {a(1)=0, a(2)=2, (-2*n+2*n^3-4+4*n^2)*a(n)+(-6*n-3*n^2)*a(n+1)+(n+1)*a(n+2)}
GAMMA(n)*n+GAMMA(n)-4*GAMMA(n)*_C[2]*n-4*GAMMA(n)*_C[2]+_C[2]*2^(n+1)*GAMMA(n)*n+_C[2]*2^(n+1)*GAMMA(n)
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MAPLE
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spec := [S, {B=Sequence(Z, 1 <= card), C=Cycle(B), S=Prod(Z, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A138740 A158883 A052860 this_sequence A036243 A033917 A004103
Adjacent sequences: A052837 A052838 A052839 this_sequence A052841 A052842 A052843
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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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