$\lambda$-quiddit{é} sur certains sous-groupes monog{è}nes de $\mathbb{C}$

During the study of Coxeter’s friezes, M. Cuntz defined the concept of $\lambda$-quiddities and gave the problem of studying them over some subsets of $\mathbb{C}$. The objective of this text is to carry out this study in the case of some cyclic subgroups of ($\mathbb{C},+$). In particular we will study the case of the cyclic subgroups generated by $\sqrt{k}$ and $i\sqrt{k}$, with $k\in \mathbb{N}$.