Formula
Eccovi una formula, precisamente la 10.4.64 del formulario Abramowitz-Stegun
$$ \mbox{Bi} (-z) \sim \pi^{-\frac{1}{2}} z^{-\frac{1}{4}} \left[ \cos\left( \zeta+\frac{\pi}{4} \right) \sum_{0}^{\infty} (-1)^k c_{2k}\zeta^{-2k}
+ \sin \left(\zeta + \frac{\pi}{4}\right) \sum_{0}^{\infty} (-1)^k c_{2k+1}\zeta^{-2k-1} \right] \qquad(|\mbox{arg}~z| < \tfrac{2}{3} \pi) $$