The descent set polynomial revisited

We continue to explore cyclotomic factors in the descent set polynomial Qn(t), which was introduced by Chebikin, Ehrenborg, Pylyavskyy and Readdy. We obtain large classes of factors of the form Φ2s or Φ4s where s is an odd integer, with many of these being of the form Φ2p where p is a prime. We also show that if Φ2 is a factor of Q2n(t) then it is a double factor. Finally, we give conditions for an odd prime power q=pr for which Φ2p is a double factor of Q2q(t) and of Qq+1(t).