Modified Bessel K
From specialfunctionswiki
The modified Bessel function of the second kind is defined by $$K_{\nu}(z)=\dfrac{\pi}{2} \dfrac{I_{-\nu}(z)-I_{\nu}(z)}{\sin(\nu \pi)},$$ where $I_{\nu}$ is the modified Bessel function of the first kind.
Domain coloring of $K_1$.
Properties
Relationship between Airy Ai and modified Bessel K