@article{JIS_2009__12_3_a6,
     author = {Gerhold,  Stefan},
     title = {The shape of the value sets of linear recurrence sequences},
     journal = {Journal of integer sequences},
     year = {2009},
     volume = {12},
     number = {3},
     zbl = {1258.11016},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2009__12_3_a6/}
}