@article{JIS_2007__10_6_a7,
     author = {Doignon, Jean-Paul and Labarre, Anthony},
     title = {On {Hultman} numbers},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {10},
     number = {6},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2007__10_6_a7/}
}