The free Eggert-operad and an operadic description of groups

An Eggert-operad is a variant of Mac Lane’s notion of a PROP, for which not only bijective maps, but all maps between standard finite sets, are part of the structure. We construct the free Eggert-operad and prove the universal property it satisfies. Further we use the free Eggert-operad to define the Eggert-operad ${\mathrm{G}\mathrm{R}\mathrm{O}\mathrm{U}\mathrm{P}}_0^{\mathrm{f}\mathrm{p}}$ via generators and relations and show that a ${\mathrm{G}\mathrm{R}\mathrm{O}\mathrm{U}\mathrm{P}}_0^{\mathrm{f}\mathrm{p}}$-algebra is a group and vice versa. At the end we prove operadic versions of some elementary facts about groups.