Calculations of sub-μhartree accuracy employing explicitly correlated Gaussian lobe functions produce comprehensive data on the energy E(ω), its components, and the one-electron properties of the two lowest-energy states of the three-electron harmonium atom. The energy computations at 19 values of the confinement strength ω ranging from 0.001 to 1000.0, used in conjunction with a recently proposed robust interpolation scheme, yield explicit approximants capable of estimating E(ω) and the potential energy of the harmonic confinement within a few tenths of μhartree for any ω ⩾ 0.001, the respective errors for the kinetic energy and the potential energy of the electron-electron repulsion not exceeding 2 μhartrees. Thanks to the correct ω → 0 asymptotics incorporated into the approximants, comparable accuracy is expected for values of ω smaller than 0.001. Occupation numbers of the dominant natural spinorbitals and two different measures of electron correlation are also computed

The work of one of the authors (K. S.) has been financed by the statutory activity subsidy from the Polish Ministry of Science and Higher Education to the Faculty of Chemistry of Wroclaw University of Technology ("Experimental and theoretical studies of molecular systems and nanostructures," contract no. S10088). Another author (E. M.) acknowledges financial support from the Marie Curie IntraEuropean Fellowship (grant agreement PIEF-GA-2008-221734), the Career Integration Grant (grant agreement PCIG09-GA-2011-294240), and the Spanish MICINN (project no. CTQ2011-23156/BQU). Calculations reported in this paper have been carried out at the Wroclaw Centre for Networking and Supercomputing (http://www.wcss.wroc.p1) and on the MareNostrum supercomputer of the Barcelona Supercomputing Center. The authors thankfully acknowledge computer resources, technical expertise, and assistance provided by the staff of the latter institution