  Inspired by the observed $X(2900)$, we study systematically the mass spectra
of the ground pentaquark states with the $qqqq\bar{Q}$ ($Q=c,b$; $q=n,s$;
$n=u,d$) configuration in the framework of the Chromomagnetic Interaction
model. We present a detailed analysis of their stabilities and decay behaviors.
Our results indicate that there may exist narrow states or even stable states.
We hope that the present study may inspire experimentalist's interest in
searching for such a type of the exotic pentaquark state.
