Low-symmetry groups: $C_1$, $C_\mathrm{s}$, $C_\mathrm{i}$
$$\begin{array}{c|c} \hline C_1 & E \\ \hline \mathrm{A} & 1 \\ \hline \end{array}$$
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$$\begin{array}{c|cc|cc} \hline C_\mathrm{s} (= C_\mathrm{h}) & E & \sigma_\mathrm{h} & & \\ \hline \mathrm{A'} & 1 & 1 & x,y, R_z & x^2, y^2, z^2, xy \\ \mathrm{A''} & 1 & -1 & z, R_x, R_y & xz, yz \\ \hline \end{array}$$
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$$\begin{array}{c|cc|cc} \hline C_\mathrm{i} (= S_2) & E & i & & \\ \hline \mathrm{A_g} & 1 & 1 & R_x, R_y, R_z & x^2, y^2, z^2, xy, xz, yz \\ \mathrm{A_u} & 1 & -1 & x,y,z & \\ \hline \end{array}$$