Hankel H (1)
From specialfunctionswiki
The Hankel functions of the first kind are defined by $$H_{\nu}^{(1)}(z)=J_{\nu}(z)+iY_{\nu}(z),$$ where $J_{\nu}$ is the Bessel function of the first kind and $Y_{\nu}$ is the Bessel function of the second kind. Note the similarity of these functions to the Hankel functions of the second kind.
Domain coloring of analytic continuation of $H_1^{(1)}(z)$.
Bessel functions from Abramowitz&Stegun