A rank 18 Waring decomposition of $sM_{\langle 3\rangle}$ with 432 symmetries
  The recent discovery that the exponent of matrix multiplication is determined
by the rank of the symmetrized matrix multiplication tensor has invigorated
interest in better understanding symmetrized matrix multiplication. I present
an explicit rank 18 Waring decomposition of $sM_{\langle 3\rangle}$ and
describe its symmetry group.
