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@article{JIS_2005__8_2_a2, author = {Gessel, Ira M. and Xin, Guoce}, title = {A combinatorial interpretation of the numbers $6(2n)!/n!(n+2)!$}, journal = {Journal of integer sequences}, publisher = {mathdoc}, volume = {8}, number = {2}, year = {2005}, language = {en}, url = {http://geodesic.mathdoc.fr/item/JIS_2005__8_2_a2/} }
Gessel, Ira M.; Xin, Guoce. A combinatorial interpretation of the numbers $6(2n)!/n!(n+2)!$. Journal of integer sequences, Tome 8 (2005) no. 2. http://geodesic.mathdoc.fr/item/JIS_2005__8_2_a2/