Representative sample of the inflation potentials allowed at the 95% CL, when the potential is Taylor-expanded at order n = 2, 3, and 4 and trusted until the end of inflation, and under the assumption of N_* = 55 e-folds of inflation between Hubble-radius crossing for the pivot scale and the end of inflation. In natural units (where ). Left panels: full potential from the beginning of the observable window till the end of inflation. Right: zoom on the observable window directly constrained by inflation. Top: Planck TT,TE,EE+lowE. Bottom: Planck TT,TE,EE+lowE+lensing+BK15. Note that there is another branch of solutions that is symmetric under ϕ → −ϕ.