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Search: id:A002992
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| A002992 |
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Number of n-node trees with a forbidden limb of length 6.
(Formerly M0778)
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+0
18
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| 1, 1, 1, 1, 2, 3, 6, 10, 22, 45, 102, 226, 531, 1253, 3044, 7456, 18604, 46798, 119133, 305567, 790375, 2057523, 5390759, 14200122, 37598572, 100005401, 267131927, 716318650, 1927758155, 5205240762, 14098580633, 38296720823, 104308468102
(list; graph; listen)
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OFFSET
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0,5
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COMMENT
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A tree with a forbidden limb of length k is a tree where the path from any leaf inward hits a branching node or another leaf within k steps.
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REFERENCES
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A. J. Schwenk, Almost all trees are cospectral, pp. 275-307 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.
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LINKS
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Index entries for sequences related to trees
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FORMULA
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G.f.: 1+B(x)+(B(x^2)-B(x)^2)/2 where B(x) is g.f. of A052329.
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CROSSREFS
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Cf. A002955, A002988-A002991, A052318-A052329.
Sequence in context: A032202 A125702 A052817 this_sequence A130867 A122381 A124345
Adjacent sequences: A002989 A002990 A002991 this_sequence A002993 A002994 A002995
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KEYWORD
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nonn
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AUTHOR
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njas
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EXTENSIONS
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More terms, formula and comments from Christian G. Bower (bowerc(AT)usa.net), Dec 15 1999.
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