On- and off-center helium atom in a spherical multilayer quantum dot with parabolic confinement Milagros F. Morcillo-Arencibia, José Manuel Alcaraz-Pelegrina, Antonio J. Sarsa and Juan M. Randazzo Eur. Phys. J. Plus, 138 5 (2023) 456 Published online: 24 May 2023 DOI: 10.1140/epjp/s13360-023-04064-4