clenspy.utils.special.expint_asymptotic

clenspy.utils.special.expint_asymptotic(nu, x, nterms=5)

Uniform large-index asymptotic of E_nu(x) (DLMF 8.20.6) with x = lambda p, p = nu:

E_p(lambda p) ~ e^{-x} / [(lambda+1) p]

sum_{k=0}^{nterms-1} A_k(lambda) / [(lambda+1)^{2k} p^k].

Parameters:

• nu (array_like) – Broadcastable; nu is the index p, x the argument.

• x (array_like) – Broadcastable; nu is the index p, x the argument.

Returns:

ndarray – E_nu(x) to the retained order.