Calculation of the binding energy of a highly excited electron in heavy Be-like ions

The binding energy of a highly excited electron (n=20–50, where n is the principal quantum number) in the Be-like ions Au⁷⁵⁺, Pb⁷⁸⁺, Bi⁷⁹⁺, and U⁸⁸⁺ is calculated in order to determine the energy of the 2p _1/2-2s transition from experiments on dielectronic recombination in Li-like ions. A formula approximating the calculated data with an error not exceeding 0.04% is proposed.