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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. 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

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Last modified June 23 07:38 EDT 2021. Contains 345395 sequences. (Running on oeis4.)