  A Feynman formula is a representation of a solution of an initial (or
initial-boundary) value problem for an evolution equation (or, equivalently, a
representation of the semigroup resolving the problem) by a limit of $n$-fold
iterated integrals of some elementary functions as $n\to\infty$. In this note
we obtain some Feynman formulae for a class of semigroups associated with
Feller processes. Finite dimensional integrals in the Feynman formulae give
approximations for functional integrals in some Feynman--Kac formulae
corresponding to the underlying processes. Hence, these Feynman formulae give
an effective tool to calculate functional integrals with respect to probability
measures generated by these Feller processes and, in particular, to obtain
simulations of Feller processes.
