TITLE: How many balls of radius 1 can be packed into a sphere of radius 10?
QUESTION [22 upvotes]: How I can calculate the maximum number of balls of radius 1 that can be packed into a sphere of radius 10?

REPLY [24 votes]: Apparently, it is still an open question for spheres of radius $n$ for $n>5$.
See A084828 in OEIS.