A number-theoretic approach to homotopy exponents of SU(n)
  We use methods of combinatorial number theory to prove that, for each $n>1$ and any prime $p$, some homotopy group $\pi_i(SU(n))$ contains an element of order $p^{n-1+ord_p([n/p]!)}$, where $ord_p(m)$ denotes the largest integer $\alpha$ such that $p^{\alpha}$ divides $m$. 
Donald M. Davis and Zhi-Wei Sun