∂ j R - a ( b ; z ) = - a w j R - a - 1 ( b + e j ; z ) \partial_{j}R_{-a}\left(\mathbf{b};\mathbf{z}\right)=-aw_{j}R_{-a-1}\left(\mathbf{b}+\mathbf{e}_{j};\mathbf{z}\right)