A tree which is not rooted, i.e., a normal tree with no node singled out for special treatment (Skiena 1990, p. 107). Free trees are sometimes known instead as unrooted trees (e.g., Harary and Palmer 1973).
Free Tree
See also
Rooted Tree, TreeExplore with Wolfram|Alpha
References
Harary, F. and Palmer, E. M. "Unrooted Trees." §3.2 in Graphical Enumeration. New York: Academic Press, pp. 55-59, 1973.Knuth, D. E. The Art of Computer Programming, Vol. 1: Fundamental Algorithms, 3rd ed. Reading, MA: Addison-Wesley, 1997.Skiena, S. Implementing Discrete Mathematics: Combinatorics and Graph Theory with Mathematica. Reading, MA: Addison-Wesley, 1990.Referenced on Wolfram|Alpha
Free TreeCite this as:
Weisstein, Eric W. "Free Tree." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/FreeTree.html