

A226594


Number of distinct characteristic polynomials of trees with n nodes.


0



1, 1, 1, 1, 2, 3, 6, 11, 22, 42, 102, 204, 488, 1078, 2723, 6403, 16479, 40313, 106135, 271295, 724455
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,5


REFERENCES

D. M. Cvetković, M. Doob and H. Sachs, Spectra of graphs. Theory and applications, Johann Ambrosius Barth, Heidelberg, 1995.


LINKS

Table of n, a(n) for n=0..20.
M. Fürer, Efficient computation of the characteristic polynomial of a tree and related tasks. AlgorithmsESA 2009, p. 1122.


PROG

(Sage) [len(Set([t.charpoly() for t in graphs.trees(n)])) for n in range(14)]


CROSSREFS

Cf. A000055.
Sequence in context: A002083 A124973 A318123 * A043327 A247968 A005578
Adjacent sequences: A226591 A226592 A226593 * A226595 A226596 A226597


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



