Recently, we succeeded in synthesizing (La0.5-xNa0.5+x)Fe2As2 ((La,Na)122) with a solid solution range of 0 <= x <= 0.35. Superconductivity was induced for 0.15 <= x <= 0.35, with the highest transition temperature T-c = 27.0 K for x = 0.3. Here, we report the synthesis and physical properties of analogous compounds (Ln(0.5-x)Na(0.5+x))Fe2As2 ((Ln,Na)122) (Ln = Ce, Pr). Samples were synthesized by precisely tuning the reaction temperature according to Ln and x. The solid solution ranges, 0.1 <= x <= 0.3 (Ln = Ce) and 0.15 <= x <= 0.25 (Ln = Pr), become narrower with increasing atomic number of Ln (which decreases the ionic radius of Ln(3+)). Bulk superconductivity emerged for 0.2 <= x <= 0.3 and 0.15 <= x <= 0.25 with the highest Tc of 25.6 K (x = 0.3) and 24.7 K (x = 0.25) for Ln = Ce and Pr, respectively. Crystal structures refined via the Rietveld analysis method showed that the (Ln,Na)122 compounds (Ln = La, Ce, Pr) with the highest Tc have almost the same As-Fe-As bond angles (similar to 107 degrees) and As heights from Fe planes (similar to 1.43 angstrom). In addition to the solid solution ranges, the phases in the samples changed depending on the ionic radius of Ln(3+). The (Ln,Na)122 phase competes with the non-superconducting CaFe4As3(143)-type phase of (Ln,Na)Fe4As3 for Ln = Ce and Pr, whereas only the (Ln,Na)122 phase was stable for Ln = La. The 143-type phase alone was observed for Ln = Nd, and neither 122- nor 143-type phases were observed for Ln = Sm and Gd.