Degree-diameter problem $N(15,7)$

The largest possible number of vertices in a graph of maximum degree $15$ and diameter $7$.

Updates

• 2008 Lower bound: $8599986$ (8,599,986)
  Loz, E., & Sirán, J. (2008). New record graphs in the degree-diameter problem. Australasian Journal of Combinatorics, 41, 63.
  [via Table of the largest known graphs of a given diameter and maximal degree - Wikipedia]