The double almost-Riordan arrays and their sequence characterization, compression, and total positivity
Tian-Xiao He · Enumerative Combinatorics and Applications · 2026
In this paper, we define double almost-Riordan arrays and show that the set of all double almost-Riordan arrays forms a group, called the double almost-Riordan group.We also obtain sequence characterizations of double almost-Riordan arrays and give their production matrices.We define compressed double almost-Riordan arrays and present their sequence characterization.Finally, we give a criterion for the total positivity of double Riordan arrays and use it to discuss the total positivity of several double almost-Riordan arrays.