Total non-negativity of some combinatorial matrices

Many combinatorial matrices — such as those of binomial coefficients, Stirling numbers of both kinds, and Lah numbers — are known to be totally non-negative, meaning that all minors (determinants of square submatrices) are non-negative. The examples noted above can be placed in a common framework: for each one there is a non-decreasing sequence $(a_1,a_2,\dots )$, and a sequence $(e_1, e_2, \ldots)$,suchthatthe$(m,k)$-entry of the matrix is the coefficient of the polynomial $(x-a_1)\cdots (x-a_k)$ in the expansion of $(x-e_1)\cdots (x-e_m)$ as a linear combination of the polynomials $1, x-a_1, \ldots, (x-a_1)\cdots(x-a_m)$. We consider this general framework. For a non-decreasing sequence $(a_1, a_2, \ldots)$weestablishnecessaryandsufficientconditionsonthesequence$(e_1, e_2, \ldots)$ for the corresponding matrix to be totally non-negative. As corollaries we obtain totally non-negativity of matrices of rook numbers of Ferrers boards, and of graph Stirling numbers of chordal graphs.