English

On a Stirling-Whitney-Riordan triangle

Combinatorics 2021-03-25 v4

Abstract

Based on the Stirling triangle of the second kind, the Whitney triangle of the second kind and one triangle of Riordan, we study a Stirling-Whitney-Riordan triangle [Tn,k]n,k[T_{n,k}]_{n,k} satisfying the recurrence relation: \begin{eqnarray*} T_{n,k}&=&(b_1k+b_2)T_{n-1,k-1}+[(2\lambda b_1+a_1)k+a_2+\lambda( b_1+b_2)] T_{n-1,k}+\\ &&\lambda(a_1+\lambda b_1)(k+1)T_{n-1,k+1}, \end{eqnarray*} where initial conditions Tn,k=0T_{n,k}=0 unless 0kn0\le k\le n and T0,0=1T_{0,0}=1. We prove that the Stirling-Whitney-Riordan triangle [Tn,k]n,k[T_{n,k}]_{n,k} is x\textbf{x}-totally positive with x=(a1,a2,b1,b2,λ)\textbf{x}=(a_1,a_2,b_1,b_2,\lambda). We show that the row-generating function Tn(q)T_n(q) has only real zeros and the Tur\'{a}n-type polynomial Tn+1(q)Tn1(q)Tn2(q)T_{n+1}(q)T_{n-1}(q)-T^2_n(q) is stable. We also present explicit formulae for Tn,kT_{n,k} and the exponential generating function of Tn(q)T_n(q) and give a Jacobi continued fraction expansion for the ordinary generating function of Tn(q)T_n(q). Furthermore, we get the x\textbf{x}-Stieltjes moment property and 33-x\textbf{x}-log-convexity of Tn(q)T_n(q) and show that the triangular convolution zn=i=0nTn,ixiyniz_n=\sum_{i=0}^nT_{n,i}x_iy_{n-i} preserves Stieltjes moment property of sequences. Finally, for the first column (Tn,0)n0(T_{n,0})_{n\geq0}, we derive some properties similar to those of (Tn(q))n0.(T_n(q))_{n\geq0}.

Cite

@article{arxiv.2008.04120,
  title  = {On a Stirling-Whitney-Riordan triangle},
  author = {Bao-Xuan Zhu},
  journal= {arXiv preprint arXiv:2008.04120},
  year   = {2021}
}

Comments

To appear in Journal of Algebraic Combinatorics

R2 v1 2026-06-23T17:45:00.769Z