@article{JIS_2015__18_11_a1,
     author = {Harrington, Joshua and Gross, Samuel S.},
     title = {Special numbers in the ring $\Bbb Z_n$},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {18},
     number = {11},
     year = {2015},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2015__18_11_a1/}
}