  We obtain a mass function solving the Tolman-Oppenheimer-Volkoff (TOV)
equation for isotropic and spherically symmetric system via homotopy
perturbation method (HPM). Using the mass function we construct a stellar model
which can be determined from the equation of state (EOS) parameter ($\omega$)
and a model parameter ($n$). With the help of Einstein field equations we
develop three solutions which can describe different properties and the
core-crust structure of neutron star (NS). Solution I is valid for NS having
the inner and outer radius near the surface of the star. The star is physical
up to the inner radius whereas negative density occurs and the energy
conditions are violated in the upper region from the inner to outer radius.
Solution II represents NS with high gravitational redshift as well as
compactification factor. All the features of NS can be given by solution III
which involves only the EOS parameter. Our model predicts maximum mass for a NS
with the central density $5.5\times10^{15}~g/cm^{3}$ and surface redshift 0.69
is to be $2.01~M_\odot$ for the EOS parameter $\omega=0.73$. The predicted
range for the surface redshift is $0.57<Z_s<1.95$ for the allowed ranges
$8.4<n<10.9$ and $1/3<\omega<1$ in the presented NS model.
