4 elusive 'mini-Neptune' exoplanets discovered in a cosmic game of hide-and-seek

"TESS spotted single transits of two of the exoplanets, TOI 5678 b and HIP 9618 c — which are about 4.9 and 3.4 times the size of Earth, respectively — as they moved in front of their parent stars. But these observations alone were insufficient to confirm the presence of the planets...Using the same technique, the astronomers also identified two other similar mini-Neptunes, HD 15906 b and c, in another planetary system. HD 15906 b has a diameter of around 2.3 times that of Earth and orbits its orange dwarf star every 11 Earth days, while HD 15906 c has a diameter of just under three times that of Earth and seems to orbit the same star farther out, circling it in about 22 Earth days."

Our Neptune is about 3.88 times earth radii size. Using the exoplanet.eu site, now 5401 confirmed and radii size 2 to 5 earth radii, 1478 exoplanets report for duty :) http://exoplanet.eu/
The 1478 exoplanets in that radii size, min semi-major axis = 0.0044 au and max 1.54 au. 770 show semi-major axis properties from the MS SQL query. Our solar system configuration is very different than what is seen in this exoplanet radii range, example Mercury out to 2 or 3 au distance from the Sun.