“…The present paper is motivated by the question for which radii there are jammed configurations of n spheres in the d-dimensional unit cube. Many authors have studied densest packings of 50 -100 spheres in squares, triangles, disks and the cube, for certain numbers of spheres also with computer-aided proofs of optimality, see for example [4,9,13,16,24,25,26,27] and the references therein. Nurmela and Östergaard [25] achieved this by minimizing the (smooth) discrete Riesz s-energy of a configuration x of sphere centers x i (for more details on the notation see definition (1) below)…”