Degree-diameter problem $N(8,3)$
The largest possible number of vertices in a graph of maximum degree $8$ and diameter $3$.
Lower bound:
$253$
Upper bound:
Unknown
Updates
-
1995
Lower bound: $253$
Margarida Mitjana and Francesc Comellas in 1995
[via Table of the largest known graphs of a given diameter and maximal degree - Wikipedia]