Reciprocal-amplitude Laplace integral (source code)

= Reciprocal-amplitude Laplace integral

Expanding $(1+t)^{-1}$ at the endpoint and applying Watson's lemma gives
$$
\int_0^\infty\frac{e^{-xt}}{1+t}\,dt
\sim\sum_{n=0}^\infty(-1)^n n!x^{-n-1}
\qquad(x\to+\infty).
$$