Let $R$ be a commutative, associative ring with $1$ and let $\tau: R[x^{\pm 1}]\to R[x^{\pm 1}]$ be the $R$-algebra involution $\tau(x)=x^{-1}.$ Then it is natural to ask which elements of the invariant subalgebra $R[x^{\pm 1}]^\tau$ are of the form $p\cdot \tau(p)$ for some $p\in R[x^{\pm 1}]$. 

This problem reduces to a question whether each $a_n(x^n+x^{-n})+ ... + a_1(x+x^{-1})+a_0\in R[x^{\pm 1}]^\tau$ in the form
$p(x)p(x^{-1}),$ for some $p(x)=\sum_{i=0}^n c_ix^i$, which leads to the system of equations:
$$\begin{cases} c_0^2+...+c_n^2=a_0\\ c_0c_1+...+c_{n-1}c_n=a_1\\ ...\\ c_0c_n=a_n.
\end{cases}
$$

I suspect that this problem has been studied already and I am hoping to be pointed in the right direction.
I expect that this system have a solution for algebraically closed fields $R$ (at least when characteristic $\ne 2$), but don't know the proof. 
However, the most interesting case for me is $R=\mathbb Z$.