You have 15 spheres with d=1. Put all spheres in the box which has 2.6 length for each edge.
If you add new sphere, you make the new world records. It only fills 44.7% of the box!
You have 66 spheres with d=1. Put all spheres in the box which has 4 length for each edge.
If you add new sphere, you make the new world records. It only fills 54% of the box!
The answer of 64 balls. How to plot 3D all 64 balls without traces for ball to ball is a good try.
