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A052866
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A simple grammar.
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0
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1, 2, 5, 19, 97, 621, 4771, 42673, 434673, 4959433, 62569891, 863989941, 12949163833, 209203422013, 3622195815603, 66881477554921, 1311357008557921, 27202303879342353, 595035842021131843
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 835
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FORMULA
| E.g.f.: (-x-exp(-x/(-1+x))+exp(-x/(-1+x))*x)/(-1+x)
Recurrence: {a(0)=1, a(1)=2, a(2)=5, (-n^3-2*n-3*n^2)*a(n)+(3*n^2+10*n+8)*a(n+1)+(-3*n-7)*a(n+2)+a(n+3)}
a(n) = n!+A000262(n). - Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 29 2002
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MAPLE
| spec := [S, {B=Sequence(Z, 1 <= card), C=Set(B), S=Union(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A020015 A188914 A049984 * A007003 A020117 A054687
Adjacent sequences: A052863 A052864 A052865 * A052867 A052868 A052869
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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