a = − n − 2 π ⁢ z ⁢ n − 2 ⁢ z π 2 + 1 2 ⁢ b + 1 4 + z 2 ⁢ ( 1 3 − 4 ⁢ π − 2 ) + z − ( b − 1 ) 2 + 1 4 4 ⁢ π ⁢ z ⁢ n + O ⁡ ( 1 n ) a=-n-{\frac {2}{\pi }}{\sqrt {zn}}-{\frac {2z}{\pi ^{2}}}+{\tfrac {1}{2}}b+{\tfrac {1}{4}}+{\frac {z^{2}\left({\frac {1}{3}}-4\pi ^{-2}\right)+z-(b-1)^{2}+{\frac {1}{4}}}{4\pi {\sqrt {zn}}}}+{\mathcal {O}}\left({\frac {1}{n}}\right)