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Search: id:A052844
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| 1, 2, 6, 26, 148, 1032, 8464, 79592, 842832, 9914336, 128162464, 1804852128, 27489582784, 450089665664, 7880963503872, 146913179393408, 2904309329449216, 60677563647195648, 1335634021282590208
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 812
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FORMULA
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E.g.f.: exp(x*(-2+x)/(-1+x))
Recurrence: {a(0)=1, a(1)=2, a(2)=6, (-2-n^2-3*n)*a(n)+(n^2+5*n+6)*a(n+1)+(-2*n-6)*a(n+2)+a(n+3)}
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MAPLE
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spec := [S, {B=Sequence(Z, 1 <= card), C=Union(Z, B), S=Set(C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A002710 A132609 A125224 this_sequence A052859 A103937 A159311
Adjacent sequences: A052841 A052842 A052843 this_sequence A052845 A052846 A052847
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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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