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A093197 Number of labeled plane-2 trees on n triangles. +0
1
1, 6, 56, 720, 11880, 240240, 5765760, 160392960, 5079110400, 180503769600, 7117005772800, 308403583488000, 14572069319808000, 745747076954880000, 41098950018846720000, 2427001153744527360000, 152901072685905223680000 (list; graph; listen)
OFFSET

2,2

LINKS

G. Labelle, C. Lamathe and P. Leroux, A classification of plane and planar 2-trees

FORMULA

n!*(2/3*Cat(n)-1/6*Cat(n+1)), where Cat(n) is the Catalan numbers.

MAPLE

seq(mul((n+k), k=3..n), n=2..18); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Sep 14 2007

CROSSREFS

Adjacent sequences: A093194 A093195 A093196 this_sequence A093198 A093199 A093200

Sequence in context: A025749 A053336 A112699 this_sequence A052317 A122743 A137032

KEYWORD

nonn

AUTHOR

Ralf Stephan, Apr 22 2004

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Last modified October 13 09:05 EDT 2008. Contains 145008 sequences.


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