The energies of all symmetrically distinct La/Pr orderings on the M(1) (perovskite) and M(2) (rocksalt) sites were calculated with DFT+U using the Bmab unit cell of LaxPr4-xNi3O10. The resulting convex energy hull is shown in Fig. . Compositions of LaPr3Ni3O10 (x=1), La2Pr2Ni3O10 (x=2) and La3PrNi3O10 (x=3) are observed as stable phases on the hull. The lowest energy ordering for each structure are shown in Fig. . In all of the low energy structures on the hull, Pr preferentially occupies the M(2) site in the rocksalt layer.