Comparison at z = 0 of the halo mass function for different configurations of the initial conditions (see Section 3) with respect to the higher-resolution reference simulations (see Section 3.3). The upper panel shows the results for the f_NL = 0 simulations, while the lower panel shows the case with f_NL = 100. The line colour encodes the LPT order used for the initial conditions (red: 1LPT, green: 2LPT, and blue: 3LPT), while the line styles indicate the initial redshift. The dashed vertical lines show the limit of 20 particles per halo; the limit of 100 is indicated by the dash-dotted vertical lines. The shaded regions indicate the 1% difference around the reference simulation. Starting the simulation at lower redshifts improves the convergence towards the high-resolution reference.