On enumeration of $l$-hypermaps

The $l$-hypermaps, $l\ge 2$, which generalize (dual of) ribbon graphs ($l=2$ case), are interesting enumerative objects. In this paper, based on a theorem of Carlet–van de Leur–Posthuma–Shadrin and the matrix-resolvent method, we derive an explicit formula for $k$-point generating series of enumeration of $l$-hypermaps, which generalizes the one obtained in [30] for the $l=2$ case. We also generalize a theorem of Dubrovin [29].