  To avoid problems with infinite measure, the functional integral for harmonic
oscillator can be calculated by time - slicing method with continuum limit
procedure proposed Gelfand and Yaglom. In previous article we proved by
nonperturbative calculation the generalized Gelfand-Yaglom equation for
anharmonic oscillator with positive or negative mass term. In this article we
prove by step-by-step the calculation of the correction function to the
Gelfand-Yaglom equation for an-harmonic oscillator.
