A formula to construct all involutions in Riordan matrix groups (Q2404982)

The authors explain: ``The elements of the Riordan group are those matrices whose columns are the coefficients of successive terms of a geometric progression in \(\mathbb{K}[[x]]\). The initial term is a formal power series of order 0 and the common ratio is a formal power series of order 1.'' After obtaining results on finite Riordan matrices, the authors prove a number of results on involutions, such as ``linked involutions'', ``Riordan involution's formula'', ``applications of Riordan involution's formula'', and ``self dual involutions''; they show that \textit{T.-X. He}'s conjecture [Linear Algebra Appl. 496, 331--350 (2016; Zbl 1331.05015)] is true.