Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A002991
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A002991 Number of n-node trees with a forbidden limb of length 5.
(Formerly M0725)
+0
2
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)
OFFSET

0,5

COMMENT

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.

REFERENCES

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.

LINKS

Index entries for sequences related to trees

FORMULA

G.f.: 1+B(x)+(B(x^2)-B(x)^2)/2 where B(x) is g.f. of A052328.

CROSSREFS

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

KEYWORD

nonn

AUTHOR

njas

EXTENSIONS

More terms, formula and comments from Christian G. Bower (bowerc(AT)usa.net), Dec 15 1999.

page 1

Search completed in 0.002 seconds

Lookup | Welcome | Find friends | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
More pages | Superseeker | Maintained by N. J. A. Sloane (njas@research.att.com)

Last modified September 7 23:08 EDT 2008. Contains 143486 sequences.


AT&T Labs Research