Acknowledgements

The author would like to thank his friend and colleague Prof. Carlos Eugênio Imbassay Carneiro, for all his interest and help, as well as his helpful criticism regarding this work.

The author would like to thank Prof. Martin E. Muldoon, of the Department of Mathematics and Statistics of York University, for drawing his attention to the fact that there is a whole mathematical literature on these sums, which are known in that literature as Rayleigh functions.