  We consider an addition of the term which is a square of the scalar curvature
to the Einstein-Hilbert action. Under this generalized action, we attempt to
explain i) the flat rotation curves observed in spiral galaxies, which is
usually attributed to the existence of dark matter, and ii) the contradicting
observations of uniform cosmic microwave background and non-uniform galaxy
distributions against redshift. For the former, we attain the flatness of
velocities, although the magnitudes remain about half of the observations. For
the latter, we obtain a solution with oscillating Hubble parameter under
uniform mass distributions. This solution leads to several peaks of galaxy
number counts as a function of redshift with the first peak corresponding to
the Great Wall.
