  We express cluster variables of type $B_n$ and $C_n$ in terms of cluster
variables of type $A_n$. Then we associate a cluster tilted bound symmetric
quiver $Q$ of type $A_{2n-1}$ to any seed of a cluster algebra of type $B_n$
and $C_n$. Under this correspondence, cluster variables of type $B_n$ (resp.
$C_n$) correspond to orthogonal (resp. symplectic) indecomposable
representations of $Q$. We find a Caldero-Chapoton map in this setting. We also
give a categorical interpretation of the cluster expansion formula in the case
of acyclic quivers.
