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A131638
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Increasing binary trees having exactly two vertices with outdegree 1.
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0
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1, 11, 180, 4288, 141584, 6213288, 350400832, 24718075136, 2133652515072, 221311262045440, 27166907582280704, 3895974311462313984, 645512064907811491840, 122381396964887716078592, 26325690425815766552887296, 6377608610246241663568248832
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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REFERENCES
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M. P. Develin and S. P. Sullivant, Markov Bases of Binary Graph Models, Annals of Combinatorics 7 (2003) 441-466.
C. Poupard, Deux proprietes des arbres binaires ordonnes stricts, European J. Combin., 10 (1989), 369-374.
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LINKS
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Table of n, a(n) for n=1..16.
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FORMULA
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E.g.f. = (3*sec(x/sqrt(2))^2*tan(x/sqrt(2))^2-x*sec(x/sqrt(2))^2*tan(x/sqrt(2))/(sqrt(2)))/2. - Michel Marcus, Mar 03 2013
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PROG
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lista(m) = { default(realprecision, 30); x = y + O(y^m); egf = (3*tan(x/sqrt(2))^2/cos(x/sqrt(2))^2-x*tan(x/sqrt(2))/(sqrt(2)*cos(x/sqrt(2))^2))/2; forstep (n=2, m, 2, print1(round(n!*polcoeff(egf, n, y)), ", ")); } \\ Michel Marcus, Mar 03 2013
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CROSSREFS
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Sequence in context: A101791 A140034 A162715 * A157382 A174979 A157945
Adjacent sequences: A131635 A131636 A131637 * A131639 A131640 A131641
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KEYWORD
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nonn
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AUTHOR
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Wenjin W. (wjwoan(AT)hotmail.com), Oct 03 2007
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EXTENSIONS
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More terms from Michel Marcus, Mar 03 2013
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STATUS
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approved
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