Let $u(x)=\sum_{n=0}^{\infty} u_nx^n$, where $u_n$ is the number of partitions of $n$ into at most two parts. for example, $u_4=3$ because $4$ can be partitioned into at most two parts as $4$, $3+1$, or $2+2$. use the convention that $u_0=1$. then $\frac 1{u(x)}$ is a polynomial. what polynomial is it? (enter your answer in expanded form.)