Recent results of the BNL-CCNU-Bielefeld collaboration
on the Taylor expansion of the pressure up to sixth order
in the baryon, strangeness and electric charge chemical potentials
are presented, with the focus on the QCD equation of state.
The calculations have been performed with the Highly Improved
Staggered Quark action on lattices with aspect ratio $4$ and temporal
extents ranging from $6$ to $16$, i.e. at four different values of
the lattice spacing.
The strange quark mass has been tuned to its physical value, and
two ratios of the light to the strange mass, $m_l/m_s = 1/20$
and $1/27$ have been investigated.
The comparison of sixth order Taylor expansion in the chemical potentials
with fourth order ones shows that the truncation errors are small at least
up to baryon chemical potential of $\mu_B/T \simeq 2$.