Asymptotics of coefficients of multivariate generating functions: improvements for smooth points. Raichev, A. & Wilson, M. C. Electronic Journal of Combinatorics, 2008.
Asymptotics of coefficients of multivariate generating functions: improvements for smooth points [link]Paper  abstract   bibtex   
Let $∑_{β∈ℕ^d} F_β x^β$ be a multivariate power series, a generating function for a combinatorial class perhaps. Assume that in a neighborhood of the origin this series represents a nonentire function $F=G/H^p$ where $G$ and $H$ are holomorphic and $p$ is a positive integer. Given a direction $α∈ℕ_+^d$ for which asymptotics are controlled by a smooth point of the singular variety $H = 0$, we compute the asymptotics of $F_{nα}$ as $n\to∞$. We do this via multivariate singularity analysis and give an explicit formula for the full asymptotic expansion. This improves on earlier work of R. Pemantle and the second author, and allows for much more accurate numerical approximation, as demonstrated in our examples.

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