Robert Donaghey, Louis W. Shapiro. Motzkin Numbers. Journal of Combinatorial Theory, Series A, 23(3):291-301, 1977.
@article{DonagheyS77,
title = {Motzkin Numbers},
author = {Robert Donaghey and Louis W. Shapiro},
year = {1977},
researchr = {https://researchr.org/publication/DonagheyS77},
cites = {0},
citedby = {0},
journal = {Journal of Combinatorial Theory, Series A},
volume = {23},
number = {3},
pages = {291-301},
}