A242953 - OEIS

A242953

Number of connected graphs on n vertices whose spectrum has fewer than n distinct eigenvalues.

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).

KEYWORD

nonn,more

AUTHOR

EXTENSIONS

Corrected, original description as the "non-real spectrum" was incorrect, by Travis Hoppe, Mar 23 2015

STATUS

approved