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A136795
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Number of unlabeled marked trees with n nodes.
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1
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2, 6, 20, 112, 662, 4596, 34032, 268280, 2201634, 18679362, 162611904, 1446148032, 13090979394, 120303384120, 1119971272340, 10544483234056, 100261309326082, 961692928106614, 9296529143261548, 90497666895840376
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listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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A marked tree is a tree where each node and edge is marked as + or -.
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REFERENCES
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F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 293 (4.1.60).
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LINKS
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FORMULA
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G.f.: B(x) - B(x)^2 + B(x^2) where B(x) is g.f. of A136794.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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