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A052859
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A simple grammar.
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1
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1, 0, 2, 6, 26, 150, 962, 6846, 54266, 471750, 4439762, 44911086, 485570186, 5581383990, 67890295202, 870493380126, 11726471352986, 165475293394470, 2439632685738482, 37491028556508366, 599285435979866666
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| a(n) is the number of ways to select a nonempty proper subset from each block of the set partitions of {1,2,...,n}. - Geoffrey Critzer, Jan 20 2012
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 827
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FORMULA
| E.g.f.: exp(exp(x)^2-2*exp(x)+1).
Stirling transform of unsigned Hermite numbers: Sum_{k=0..n} Stirling2(n, k)*|HermiteH(k, 0)|. - Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 12 2003
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MAPLE
| spec := [S, {B=Prod(C, C), C=Set(Z, 1 <= card), S=Set(B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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MATHEMATICA
| nn=20; a=Exp[x]-1; Range[0, nn]! CoefficientList[Series[Exp[a^2], {x, 0, nn}], x] (* Geoffrey Critzer, Jan 20 2012 *)
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CROSSREFS
| Cf. A067994.
Sequence in context: A168450 A125224 A052844 * A103937 A159311 A000629
Adjacent sequences: A052856 A052857 A052858 * A052860 A052861 A052862
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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