@article{JIS_2015__18_10_a3,
     author = {Rowell,  Jonathan T.},
     title = {Solution sequences for the keyboard problem and its generalizations},
     journal = {Journal of integer sequences},
     year = {2015},
     volume = {18},
     number = {10},
     zbl = {1329.11109},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2015__18_10_a3/}
}