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Search: id:A002991
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| A002991 |
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Number of n-node trees with a forbidden limb of length 5.
(Formerly M0725)
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+0
2
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| 1, 1, 1, 1, 2, 3, 5, 10, 21, 43, 97, 215, 503, 1187, 2876, 7033, 17510, 43961, 111664, 285809, 737632, 1915993, 5008652, 13163785, 34774873, 92282214, 245930746, 657931603, 1766481135, 4758553683, 12858286083, 34844908142, 94681272368
(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 A052328.
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CROSSREFS
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Cf. A002955, A002988-A002992, A052318-A052329.
Sequence in context: A132418 A024494 A131708 this_sequence A022861 A001646 A103595
Adjacent sequences: A002988 A002989 A002990 this_sequence A002992 A002993 A002994
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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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