A051427 Number of strictly Deza graphs with n nodes.

0, 0, 0, 0, 0, 0, 0, 3, 2, 1, 0, 6, 1, 1, 1

Offset

1,8

Comments

From the Erikson et al. paper: We consider the following generalization of strongly regular graphs. A graph G is a Deza graph if it is regular and the number of common neighbors of two distinct vertices takes on one of two values (not necessarily depending on the adjacency of the two vertices). - Jonathan Vos Post, Jul 06 2008

Links

Table of n, a(n) for n=1..15.

M. Erickson, S. Fernando, W. H. Haemers, D. Hardy and J. Hemmeter, Deza graphs: A generalization of strongly regular graph, J. Combinatorial Designs, Vol 7, Issue 6, 395-405, Oct 21, 1999. See also here.

Sean A. Irvine, Java program (github)

Crossrefs

Cf. A005176, A076434, A076435, A088741.

Sequence in context: A179753 A279318 A084269 * A194763 A194741 A194753

Adjacent sequences: A051424 A051425 A051426 * A051428 A051429 A051430

Keyword

nonn,nice,hard,more

Author

N. J. A. Sloane

Extensions

a(14)-a(15) from Sean A. Irvine, Sep 18 2021

Status

approved