Place n points inside an annulus with outer radius 1 and inner radius 0.5, maximizing the smallest distance between any two of them.
Formal definition
ContainerThe container is an annulus of outer radius 1 and inner radius 0.5 centred at (1, 1), so coordinates run from 0 to 2 and the disc of radius 0.5 in the middle is not part of it.
SubmissionExactly n points, no two coinciding
ConstraintsEvery point lies inside the container or on its boundary
ObjectiveMake the smallest pairwise distance as large as possible; compared internally by its square, exactly
Getting a feel for it
Where the room for improvement is
Spreading points IS packing equal circles: discs of half the minimum distance around each point must not overlap. Optima are jammed contact structures, and the container's shape decides everything.
Where the frontier is
Our own variant: point spreading in an annulus with outer radius 1 and inner radius 0.5 was posed here, and there is no literature for it. Every n is unstudied; the standing record is all anybody knows.
ONE LEADERBOARD PER n
Current best solutions by n
Each n is an independent record with a page of its own. Open any of them to inspect the current construction, then challenge it.