  We elaborate on the inflationary model starting from multidimensional
Lagrangian and gravity with second-order curvature terms. The effective scalar
field is related to the Ricci scalar of extra dimensions. It is shown that the
Kretschmann and the Ricci tensor square terms dominate during inflation. The
observable values of the spectral index and the tensor-to-scalar ratio are
obtained for specific values of the model parameters.
