OFFSET
0,5
REFERENCES
D. M. Cvetković, M. Doob and H. Sachs, Spectra of graphs. Theory and applications, Johann Ambrosius Barth, Heidelberg, 1995.
LINKS
M. Fürer, Efficient computation of the characteristic polynomial of a tree and related tasks. Algorithms-ESA 2009, p. 11-22.
PROG
(Sage) [len(Set([t.charpoly() for t in graphs.trees(n)])) for n in range(14)]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
F. Chapoton, Jun 13 2013
EXTENSIONS
a(0) = 1 added by Peter Luschny, Mar 01 2020
a(17)-a(20) from F. Chapoton, Mar 02 2020
STATUS
approved