@article{JIS_2004__7_3_a6,
     author = {Pfeiffer,  G\"otz},
     title = {Counting transitive relations},
     journal = {Journal of integer sequences},
     year = {2004},
     volume = {7},
     number = {3},
     zbl = {1071.06003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2004__7_3_a6/}
}