Generalized Riordan arrays

In this paper, we generalize the concept of Riordan array. A generalized Riordan array with respect to cncn is an infinite, lower triangular array determined by the pair (g(t),f(t))(g(t),f(t)) and has the generic element dn,k=[tn/cn]g(t)(f(t))k/ckdn,k=[tn/cn]g(t)(f(t))k/ck, where cncn is a fixed sequence of non-zero constants with c0=1c0=1.We demonstrate that the generalized Riordan arrays have similar properties to those of the classical Riordan arrays. Based on the definition, the iteration matrices related to the Bell polynomials are special cases of the generalized Riordan arrays and the set of iteration matrices is a subgroup of the Riordan group. We also study the relationships between the generalized Riordan arrays and the Sheffer sequences and show that the Riordan group and the group of Sheffer sequences are isomorphic. From the Sheffer sequences, many special Riordan arrays are obtained. Additionally, we investigate the recurrence relations satisfied by the elements of the Riordan arrays. Based on one of the recurrences, some matrix factorizations satisfied by the Riordan arrays are presented. Finally, we give two applications of the Riordan arrays, including the inverse relations problem and the connection constants problem.