  The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the
onset of deconfinement in strongly interacting matter through a beam energy
scan of particle production in collisions of nuclei of varied sizes. This paper
presents results on inclusive double-differential spectra, transverse momentum
and rapidity distributions and mean multiplicities of $\pi^\pm$, $K^\pm$, $p$
and $\bar{p}$ produced in $^{40}$Ar+$^{45}$Sc collisions at beam momenta of
13$A$, 19$A$, 30$A$, 40$A$, 75$A$ and 150$A$~\GeVc. The analysis uses the 10\%
most central collisions, where the observed forward energy defines centrality.
The energy dependence of the $K^\pm$/$\pi^\pm$ ratios as well as of inverse
slope parameters of the $K^\pm$ transverse mass distributions are placed in
between those found in inelastic $p$+$p$ and central Pb+Pb collisions. The
results obtained here establish a system-size dependence of hadron production
properties that so far cannot be explained either within statistical or
dynamical models.
