中央研究院 数學研咒所 S-path and S-nonnegative path Let s be a finite subset of zo Xa(0,0) An S-path is a lattice pat th (x1y1)(x2y2).(x2yk) with(xpy)∈S An S-nonnegative path is an S-path in the first quadrant 第10页第10页 S-path and S-nonnegative path • Let S be a finite subset of Z≥0×Z\{(0,0)}. • An S-path is a lattice path (x1 ,y1 )(x2 ,y2 )…(xk ,yk ) with (xi ,yi )∈S. • An S-nonnegative path is an S-path in the first quadrant