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A052871
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A simple grammar.
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1
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0, 1, 4, 27, 268, 3585, 60846, 1255471, 30535912, 855688833, 27148954330, 962037575631, 37659124454700, 1613921425656865, 75156944627712598, 3778932799275876495, 204039148080188427856, 11774630933193827543553
(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 842
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FORMULA
| E.g.f.: -LambertW(x/(-1+x))
a(n) = Sum_{k=1..n} (n!/k!)*binomial(n-1, k-1)*k^(k-1). - Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 17 2003
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MAPLE
| spec := [S, {C=Sequence(Z, 1 <= card), B=Set(S), S=Prod(B, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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PROG
| (Maxima) makelist(sum((n!/k!)*binomial(n-1, k-1)*k^(k-1), k, 1, n), n, 0, 17); [Bruno Berselli, May 25 2011]
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CROSSREFS
| Cf. A008297, A060356.
Sequence in context: A052813 A121353 A161633 * A104653 A194787 A020558
Adjacent sequences: A052868 A052869 A052870 * A052872 A052873 A052874
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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