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A052868
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A simple grammar.
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0
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1, 1, 5, 40, 449, 6556, 118507, 2561518, 64540625, 1859206600, 60309007091, 2176222795594, 86488677518905, 3754431762036892, 176771908657345835, 8973513955735900246, 488586200931213192353, 28404347922603101834512
(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 839.
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FORMULA
| E.g.f.: LambertW(x/(-1+x))/x*(-1+x)
a(n) = Sum_{k=0..n} n!/k!*binomial(n-1, k-1)*(k+1)^(k-1). - Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 17 2003
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MAPLE
| spec := [S, {C=Sequence(Z, 1 <= card), S=Set(B), B=Prod(C, S)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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PROG
| (Maxima) makelist(if n=0 then 1 else sum(n!/k!*binomial(n-1, k-1)*(k+1)^(k-1), k, 0, n), n, 0, 17); [Bruno Berselli, May 25 2011]
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CROSSREFS
| Sequence in context: A034000 A000359 A121886 * A094574 A090362 A201366
Adjacent sequences: A052865 A052866 A052867 * A052869 A052870 A052871
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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