Lonesum decomposable matrices

A lonesum matrix is a $(0,1)$-matrix that is uniquely determined by its row and column sum vectors. In this paper, we introduce lonesum decomposable matrices and study their properties. We provide a necessary and sufficient condition for a matrix $A$ to be lonesum decomposable, and give a generating function for the number $D_k(m,n)$ of $m\times n$ lonesum decomposable matrices of order $k$. Moreover, by using this generating function we prove some congruences for $D_k(m,n)$ modulo a prime.