中央研究院 数學研咒所 Catalan paths An n-Catalan path is a lattice path from(0,0 to(2n, O)in the first quadrant consisting of up step(l, 1)and down-step(1, -1) 第2页第2页 Catalan paths • An n-Catalan path is a lattice path from (0,0) to (2n,0) in the first quadrant consisting of up￾step (1,1) and down-step (1,-1)