@article{JIS_2001__4_2_a1,
     author = {Broughan, Kevin A.},
     title = {The gcd-sum function},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {4},
     number = {2},
     year = {2001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2001__4_2_a1/}
}