A226594 Number of distinct characteristic polynomials of trees with n nodes.

1, 1, 1, 1, 2, 3, 6, 11, 22, 42, 102, 204, 488, 1078, 2723, 6403, 16479, 40313, 106135, 271295, 724455

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. Algorithms-ESA 2009, p. 11-22.

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