Function trv::maths::eval_lanczos_approx_series#

Function Documentation#

std::complex<double> trv::maths::eval_lanczos_approx_series(std::complex<double> z)#

Evaluate the Lanczos approximation series \( A_g(z) \) for the gamma function.

The series approximate the gamma function by

\[ \Gamma(z + 1) = \sqrt{2\pi} (z + g + 1/2)^{z + 1/2} \mathrm{e}^{- z - g - 1/2} A_g(z) \]
where \( g \) is the Lanczos constant.

Parameters

z – Complex argument.

Returns

Value of \( A_g(z) \).