  We study Liouville theorems for the following polyharmonic
H\'{e}non-Lane-Emden system \begin{eqnarray*}
  \left\{\begin{array}{lcl} (-\Delta)^m u&=& |x|^{a}v^p \ \ \text{in}\ \
\mathbb{R}^n,\\ (-\Delta)^m v&=& |x|^{b}u^q \ \ \text{in}\ \ \mathbb{R}^n,
\end{array}\right.
  \end{eqnarray*} when $m,p,q \ge 1,$ $pq\neq1$, $a,b\ge0$. The main conjecture
states that $(u,v)=(0,0)$ is the unique nonnegative solution of this system
whenever $(p,q)$ is {\it under} the critical Sobolev hyperbola, i.e. $
\frac{n+a}{p+1}+\frac{n+b}{q+1}>{n-2m}$. We show that this is indeed the case
in dimension $n=2m+1$ for bounded solutions. In particular, when $a=b$ and
$p=q$, this means that $u=0$ is the only nonnegative bounded solution of the
polyharmonic H\'{e}non equation
  \begin{equation*}
  (-\Delta)^m u= |x|^{a}u^p \ \ \text{in}\ \ \mathbb{R}^{n}
  \end{equation*} in dimension $n=2m+1$ provided $p$ is the subcritical Sobolev
exponent, i.e., $1<p<{1+4m+2a}$. Moreover, we show that the conjecture holds
for radial solutions in any dimensions. It seems the power weight functions
$|x|^a$ and $|x|^b$ make the problem dramatically more challenging when dealing
with nonradial solutions.
