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Search: id:A052750
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| A052750 |
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a(n) = (2*n+1)^(n-1). E.g.f.: exp(-1/2*LambertW(-2*x)). |
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+0
2
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| 1, 1, 5, 49, 729, 14641, 371293, 11390625, 410338673, 16983563041, 794280046581, 41426511213649, 2384185791015625, 150094635296999121, 10260628712958602189, 756943935220796320321, 59938945498865420543457
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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a(n+1) is the number of labeled incomplete ternary trees on n vertices in which each left child has a larger label than its parent. - Brian Drake (bdrake(AT)brandeis.edu), Jul 28 2008
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 706
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MAPLE
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spec := [S, {B=Prod(Z, S, S), S=Set(B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
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CROSSREFS
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Sequence in context: A102773 A028575 A006554 this_sequence A145088 A062995 A104600
Adjacent sequences: A052747 A052748 A052749 this_sequence A052751 A052752 A052753
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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EXTENSIONS
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Better description from Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 02 2003
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