  The Hadamard product of two power series $\sum a_n z^n$ and $\sum b_n z^n$ is
the power series $\sum a_n b_n z^n$. We define the (Hadamard) grade of a power
series $A$ to be the least number (finite or infinite) of algebraic power
series, the Hadamard product of which equals $A$. We study and discuss this
notion.
