Numerical semigroups with concentration two

José C. Rosales, M. B. Branco, Márcio A. Traesel

We define the concentration of a numerical semigroup $S$ as $\mathsf{C}(S)=\max \left\{{\text{next}}_S(s)-s|s\in S\backslash \{0\}\right\}$ wherein $\text{next}_S(s)=\min\left\{…