  The standard Starobinsky inflation has been extended to the $R + \alpha R^n -
\beta R^{2-n}$ model to obtain a stable minimum of the Einstein frame scalar
potential of the auxiliary field. As a result we have obtained obtain a scalar
potential with non-zero value of residual vacuum energy, which may be a source
of Dark Energy. Our results can be easily consistent with PLANCK or BICEP2 data
for appropriate choices of the value of $n$.

High Energy Physics - Theory;General Relativity and Quantum Cosmology