This is − ( Γ ( 0 , − ln ⁡ 2 ) + i π ) {\displaystyle -(\Gamma \left(0,-\ln 2\right)+i\,\pi )} where Γ ( a , x ) {\displaystyle \Gamma \left(a,x\right)} is the incomplete gamma function. It must be understood as the Cauchy principal value of the function.