The analytical procedures previously developed by the authors (see references) in order to evaluate the short-range interaction energy of two protons bound by one electron are briefly reviewed. The Hamilton-Jacobi-Riccati outer equation is solved perturbatively up to fifth order in the perturbation parameter, where the zero-order function is the He + ground-state function. The inner equation is solved by expanding Hylleraas determinant. The results are consistent with those of similar treatments and with accurate numerical calculations.J. Phys. Commun. 2 (2018) 045018 M Battezzati and V Magnasco Recently analytical methods for evaluation of + H 2 interaction energies were used extensively with the help of computer algebra and combined with highly accurate numerical calculations [12,17]. They contribute to shed light on the structure and properties of the solutions. In [17] a variant of the present approach was developed in order to check numerical data, from which exact values of h.o. coefficients of the expansion were inferred by numerical interpolation.