In order to determine the first four energy levels of our anharmonic potential, we will
compute the first four eigenvalues of the anharmonic oscillator potential with a quartic term using
Heun polynomials and Maple software packages. We will then compare them to the results
obtained from the conventional perturbation method, treating the quartic term as perturbation up
to the third order. Through this it can be shown that generally the two methods agree well with
each other when the perturbing potential is weak. Nevertheless, the perturbation results will start
to deviate from those of the exact solutions at stronger perturbation potentials and higher excited
states.