(ii) hexagonal lattice, N=2: Phi = 0.12897847031832, c_H*|T| = 0.12897847031832, cell areas add to 1.732050807569 (|T| = 1.732050807569)
(iii) local minimisation of Phi/|T| (free centres and radii), 4 starts per N:
   N=1 : min Phi/|T| = 0.42550070   (c_H = 0.07446575, excess 3.51e-01)
   N=2 : min Phi/|T| = 0.07446575   (c_H = 0.07446575, excess -4.86e-16)
   N=3 : min Phi/|T| = 0.24132918   (c_H = 0.07446575, excess 1.67e-01)
   N=4 : min Phi/|T| = 0.17039563   (c_H = 0.07446575, excess 9.59e-02)
   N=6 : min Phi/|T| = 0.08496532   (c_H = 0.07446575, excess 1.05e-02)
RESULT PASS
