  We investigate cosmological perturbations generated during de Sitter
inflation in the three-coupled scalar theory. This theory is composed of three
coupled scalars ($\phi_p,p=1,2,3$) to give a sixth-order derivative scalar
theory for $\phi_3$, in addition to tensor. Recovering the power spectra
between scalars from the LCFT correlators in momentum space indicates that the
de Sitter/logarithmic conformal field theory (dS/LCFT) correspondence works in
the superhorizon limit. We use LCFT correlators derived from the dS/LCFT
differentiate dictionary to compare cosmological correlators (power spectra)
and find also LCFT correlators by making use of extrapolate dictionary. This is
because the former approach is more conventional than the latter. A bulk
version dual to the truncation process to find a unitary CFT in the LCFT
corresponds to selecting a physical field $\phi_2$ with positive norm
propagating on the dS spacetime.
