Suppose an,bn, and cn= anbn
are sequences of algebraic integers and that all bn are nonzero. It is easy to
verify that if both a(z) =∑n=0∞anzn and b(z) =∑n=0∞bnzn are rational
functions, then so is c(z) =∑n=0∞cnzn. We are interested in studying
the conjecture that if b(z) and c(z) are rational functions, then so is a(z).
We shall prove this in the case that b(z) has no more than three distinct
singularities.