  High temperature superconductivity was recently found in the bilayer
nickelate $\rm{La}_3 \rm{Ni}_2 \rm{O}_7$ (La327), followed by the discovery of
superconductivity in the trilayer $\rm{La}_4 \rm{Ni}_3 \rm{O}_{10}$ (La4310),
under high pressure. Through studying the electronic correlation of La4310 with
DFT+DMFT, and further comparing it with that of La327, we find that the $e_g$
orbitals of the outer-layer Ni cations in La4310 have a similar (but slightly
weaker) electronic correlation to those in La327, in which the electrons behave
as a non-Fermi liquid with Hund correlation and linear-in-temperature
scattering rate. Our results suggest that the experimentally observed ``strange
metal'' behavior may be explained by the Hund spin correlation featuring high
spin states and spin-orbital separation. In contrast, the electrons in the
inner-layer Ni cations in La4310 behave as a Fermi liquid. The weaker
electronic correlation in La4310 is attributed to more hole-doping, which may
explain its lower superconducting transition temperature.
