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3, 4, 12, 60, 432, 4080, 47520, 655200, 10402560, 186520320, 3723148800, 81829440000, 1962948556800, 51024208435200, 1428503479603200, 42852489039360000, 1371237803679744000, 46621373950255104000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 572
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FORMULA
| E.g.f.: -(-3+5*x)/(-1+2*x)/(-1+x)
Recurrence: {a(0)=3, a(1)=4, (2*n^2+6*n+4)*a(n)+(-6-3*n)*a(n+1)+a(n+2)=0}
(2^n+2)*n!
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MAPLE
| spec := [S, {S=Union(Sequence(Z), Sequence(Z), Sequence(Union(Z, Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
| Sequence in context: A079154 A101716 A109771 * A122903 A059792 A018930
Adjacent sequences: A052623 A052624 A052625 * A052627 A052628 A052629
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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