If a number of equal spheres be described with their centres placed in two parallel layers; with the centre of each sphere at the distance of radius x sqrt(2) or radius x 1.41421 (or at some lesser distance), from the centres of the six surrounding spheres in the same layer; and at the same distance from the centres of the adjoining spheres in the other and parallel layer;
V2 erradioko edo ? 1,41421 erradioko distantziara (edo distantzia txikixeagora) delarik, eta beste plano paraleloan aldamenean dituen esferen erdigunetik distantzia berera;