Remarks on the Vietoris sequence and corresponding convolution formulas

In this paper we consider the so-called Vietoris sequence, a sequence of rational numbers of the form ck=12k(k⌊k2⌋), k= 0, 1, ⋯. This sequence plays an important role in many applications and has received a lot of attention over the years. In this work we present the main properties of the Vietoris sequence, having in mind its role in the context of hypercomplex function theory. Properties and patterns of the convolution triangles associated with (ck)k are also presented.Research at CMAT was partially financed by Portuguese funds through FCT - Funda¸c˜ao para a Ciˆencia e a Tecnologia, within the Projects UIDB/00013/2020 and UIDP/00013/2020. Research at CIDMA has been financed by FCT, within the Projects UIDB/04106/2020 and UIDP/04106/2020

On generalized Vietoris’ number sequences

Recently, by using methods of hypercomplex function theory, the authors have shown that a certain sequence S of rational numbers (Vietoris’ sequence) combines seemingly disperse subjects in real, complex and hypercomplex analysis. This sequence appeared for the first time in a theorem by Vietoris (1958) with important applications in harmonic analysis (Askey/Steinig, 1974) and in the theory of stable holomorphic functions (Ruscheweyh/Salinas, 2004). A non-standard application of Clifford algebra tools for defining Clifford-holomorphic sequences of Appell polynomials was the hypercomplex context in which a one-parametric generalization S(n),n≥1, of S (corresponding to n=2) surprisingly showed up. Without relying on hypercomplex methods this paper demonstrates how purely real methods also lead to S(n). For arbitrary n≥1 the generating function is determined and for n=2 a particular case of a recurrence relation similar to that known for Catalan numbers is proved.The work of the first and third authors was supported by Portuguese funds through the CIDMA - Center for Research and Development in Mathematics and Applications, and the Portuguese Foundation for Science and Technology (“FCT-Fundação para a Ciência e Tecnologia”), within project PEst-OE/MAT/UI4106/2013. The work of the second author was supported by Portuguese funds through the CMAT - Centre of Mathematics and FCTwithin the Project UID/MAT/00013/201