@article{JIS_2003__6_2_a4,
     author = {Romik,  Dan},
     title = {Some formulas for the central trinomial and {Motzkin} numbers},
     journal = {Journal of integer sequences},
     year = {2003},
     volume = {6},
     number = {2},
     zbl = {1030.05002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2003__6_2_a4/}
}