Bessel Y
From specialfunctionswiki
Bessel functions (of the second kind) $Y_{\nu}$ are defined via the formula $$Y_{\nu}(z)=\dfrac{J_{\nu}(z)\cos(\nu \pi)-J_{-\nu}(z)}{\sin(\nu \pi)}.$$
Domain coloring of analytic continuation of $Y_0(z)$.
Bessel functions from Abramowitz&Stegun