The nonrelativistic energies of the homonuclear ion T-2(+) are calculated for the ground state using the Lagrange-mesh method as was done for the isotopomers H-2(+) and D-2(+) (Olivares-Pilon and Baye 2012 J. Phys. B: At. Mol. Opt. Phys. 45 065101 and Olivares-Pilon 2013 J. Phys. B: At. Mol. Opt. Phys. 46 245101). Energies and eigenfunctions are obtained up to four of the lowest bound vibrational states (v = 0, 1, 2, 3) which support 62, 61, 60, and 58 bound rotational states, respectively. Some quasibound states are also presented until L = 68. From the obtained wave functions, electric quadrupole transitions per time unit are calculated between those states over the whole rotational bands. Extensive results are presented with six significant digits. The ground state energy of the symmetric systems H-infinity(2)+, H-infinity(-), Ps(-), H-, D-, T-, mu(+)mu(+)e, and mu(+)e e is presented with high accuracy as a function of beta = m(3)(2m+ m(3)).