Observable range of the best-fit inflaton potentials, when V(φ) is Taylor expanded to the nth order around the pivot value φ_∗ in natural units (where assuming a flat prior on ϵ_V, η_V, , and and using Planck TT+lowP+BAO. Potentials obtained under the transformation (φ−φ_∗) → (φ_∗−φ) leave the same observable signature and are also allowed. The sparsity of potentials with a small V₀ = V(φ_∗) is due to our use of a flat prior on ϵ_V rather than on ln(V₀); in fact, V₀ is unbounded from below in the n = 2 and 3 results. The axis ranges are identical to those in Fig. 20, to make the comparison easier.