“…They are also useful in cryptography, information theory, and computer security by 15 providing convenient encryption and decryption methods [1]. Motivated by Shapiro's open questions [12], Riordan involutions have been intensely investigated as a combinatorial concept [4,5]. In this paper, we investigate invariant sequences by means of the eigenspaces of P D and P T D, where P is the Pascal matrix and D an infinite diagonal matrix with alternating diagonal entries in {1, −1} (see Sections 2,3).…”