  In the lightly bound Skyrme model, several Skyrmions having particularly
strong binding are clusters of unit baryon number Skyrmions arranged as
truncated tetrahedra. Their baryon numbers form the sequence B = 4, 16, 40, 80,
140, 224. This is the standard sequence of tetrahedral numbers multiplied by
four, and therefore agrees with the sequence of magic proton and neutron
numbers 2, 8, 20, 40, 70, 112 that occurs in the nuclear shell model in the
absence of strong spin-orbit coupling. This sequence includes several of the
magic numbers that are predicted for tetrahedrally deformed nuclei, and also
appears in the context of the FCC lattice geometry investigated long ago by
Wigner and revived more recently.
