N ν 2 ⁡ ( x ) ∼ 2 π ⁢ x ⁢ ( 1 − 1 2 ⁢ μ − 3 ( 2 ⁢ x ) 2 − 1 2 ⋅ 4 ⁢ ( μ − 1 ) ⁢ ( μ − 45 ) ( 2 ⁢ x ) 4 − ⋯ ) {N_{\nu }^{2}}\left(x\right)\sim {\frac {2}{\pi x}}\left(1-{\frac {1}{2}}{\frac {\mu -3}{(2x)^{2}}}-{\frac {1}{2\cdot 4}}{\frac {(\mu -1)(\mu -45)}{(2x)^{4}}}-\cdots \right)