@article{RCM_2019_53_2_a1,
     author = {Juan Triana and Rodrigo de Castro},
     title = {The formal derivative operator and multifactorial numbers},
     journal = {Revista colombiana de matematicas},
     pages = {125--137},
     publisher = {mathdoc},
     volume = {53},
     number = {2},
     year = {2019},
     url = {http://geodesic.mathdoc.fr/item/RCM_2019_53_2_a1/}
}