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A242953 Number of connected graphs on n vertices whose spectrum has fewer than n distinct eigenvalues. 1
0, 0, 1, 3, 10, 58, 314, 3798, 51609, 1716267 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
The spectrum refers to the eigenvalues of the adjacency matrix.
LINKS
Travis Hoppe and Anna Petrone, Encyclopedia of Finite Graphs
T. Hoppe and A. Petrone, Integer sequence discovery from small graphs, arXiv preprint arXiv:1408.3644, 2014
Eric Weisstein's World of Mathematics, Graph Spectrum
CROSSREFS
Cf. A064731 (integral graphs), A242952 (distinct spectrum graphs).
Sequence in context: A366696 A274585 A333031 * A112101 A159321 A181077
KEYWORD
nonn,more
AUTHOR
Travis Hoppe and Anna Petrone, May 27 2014
EXTENSIONS
Corrected, original description as the "non-real spectrum" was incorrect, by Travis Hoppe, Mar 23 2015
STATUS
approved

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Last modified March 29 07:27 EDT 2024. Contains 371265 sequences. (Running on oeis4.)