Koecher–Maass series

The Koecher–Maass series is a mathematical series that arises in the context of the theory of modular forms and automorphic forms. It is named after mathematicians Martin Koecher and Hans Maass, who contributed to the understanding of modular forms and their properties. The series itself is typically associated with the theory of modular forms on the upper half-plane. These forms are complex functions that are not only continuous but also satisfy certain transformation properties under the action of the modular group.