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A052881
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A simple grammar.
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2
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0, 0, 2, 9, 44, 250, 1644, 12348, 104544, 986256, 10265760, 116915040, 1446526080, 19323757440, 277238626560, 4251984710400, 69426608025600, 1202482800691200, 22021300630425600, 425162773111910400
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 853
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FORMULA
| E.g.f.: -ln(-1/(-1+x))*x/(-1+x)
Recurrence: {a(1)=0, a(2)=2, (n^3+3*n^2+2*n)*a(n)+(-5*n-2*n^2-2)*a(n+1)+(n+1)*a(n+2)}
a(n) = n!*Sum 1/i, i = 1..(n-1) = s(n, 2)-(n-1)! = n*s(n-1, 2) = n*a(n-1) + (n-1)! + (n-2)! = A000142(n)*A001008(n-1)/A002805(n-1) = A000254(n)-A000142(n-1) = A000027(n)*A000254(n-1) = a(n-1)*A000027(n) + A001048(n-1). - Henry Bottomley (se16(AT)btinternet.com), May 05 2001
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MAPLE
| spec := [S, {B=Sequence(Z, 1 <= card), C=Cycle(Z), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
with(combinat):a:=n->abs(stirling1(n, 2))*n: seq(a(n), n=0..19); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 05 2007
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PROG
| sage: [stirling_number1(i, 2)*i for i in xrange(0, 32)] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 27 2008
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CROSSREFS
| Sequence in context: A108308 A119855 A047119 * A020071 A000166 A093464
Adjacent sequences: A052878 A052879 A052880 * A052882 A052883 A052884
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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