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We present a combined experimental and theoretical investigation on Ca<inline-formula><math display="inline"><semantics><msup><mrow/><mo>+</mo></msup></semantics></math></inline-formula> ions in helium droplets, He<inline-formula><math display="inline"><semantics><msub><mrow/><mi>N</mi></msub></semantics></math></inline-formula>Ca<inline-formula><math display="inline"><semantics><msup><mrow/><mo>+</mo></msup></semantics></math></inline-formula>. The clusters have been formed in the laboratory by means of electron-impact ionization of Ca-doped helium nanodroplets. Energies and structures of such complexes have been computed using various approaches such as path integral Monte Carlo, diffusion Monte Carlo and basin-hopping methods. The potential energy functions employed in these calculations consist of analytical expressions following an improved Lennard-Jones formula whose parameters are fine-tuned by exploiting ab initio estimations. Ion yields of He<inline-formula><math display="inline"><semantics><msub><mrow/><mi>N</mi></msub></semantics></math></inline-formula>Ca<inline-formula><math display="inline"><semantics><msup><mrow/><mo>+</mo></msup></semantics></math></inline-formula> -obtained via high-resolution mass spectrometry- generally decrease with <i>N</i> with a more pronounced drop between <inline-formula><math display="inline"><semantics><mrow><mi>N</mi><mo>=</mo><mn>17</mn></mrow></semantics></math></inline-formula> and <inline-formula><math display="inline"><semantics><mrow><mi>N</mi><mo>=</mo><mn>25</mn></mrow></semantics></math></inline-formula>, the computed quantum He<inline-formula><math display="inline"><semantics><msub><mrow/><mi>N</mi></msub></semantics></math></inline-formula>Ca<inline-formula><math display="inline"><semantics><msup><mrow/><mo>+</mo></msup></semantics></math></inline-formula> evaporation energies resembling this behavior. The analysis of the energies and structures reveals that covering Ca<inline-formula><math display="inline"><semantics><msup><mrow/><mo>+</mo></msup></semantics></math></inline-formula> with 17 He atoms leads to a cluster with one of the smallest energies per atom. As new atoms are added, they continue to fill the first shell at the expense of reducing its stability, until <inline-formula><math display="inline"><semantics><mrow><mi>N</mi><mo>=</mo><mn>25</mn></mrow></semantics></math></inline-formula>, which corresponds to the maximum number of atoms in that shell. Behavior of the evaporation energies and radial densities suggests liquid-like cluster structures.