A178925 Number of n-node simple graphs that are determined by spectrum.

1, 2, 4, 11, 32, 146, 934, 10624, 223629, 9444562, 803666188, 134023600111

Offset

1,2

Links

Table of n, a(n) for n=1..12.

A. E. Brouwer and E. Spence, Cospectral graphs on 12 vertices, Electr. J. Combin. 16 (2009) N20.

Eric Weisstein's World of Mathematics, Determined by Spectrum

Formula

a(n) = A000088(n) - A006608(n).

Crossrefs

Cf. A000088, A006608 (simple graphs not determined by spectrum).

Sequence in context: A123424 A123449 A123404 * A298445 A294224 A296270

Adjacent sequences: A178922 A178923 A178924 * A178926 A178927 A178928

Keyword

nonn,hard,more

Author

Eric W. Weisstein, Dec 29 2010

Extensions

a(10) from Eric W. Weisstein, Dec 30 2010

a(11)-a(12) from Eric W. Weisstein, Apr 11 2024 (from Brouwer and Spence)

Status

approved