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How to obtain an asymptotic expansion of a sequence from an analytic identity satisfied by its generating function

Published online by Cambridge University Press:  09 April 2009

J. M. Plotkin
Affiliation:
Department of Mathematics, Michigan State University, East Lansing, Michigan, 48824
John W. Rosenthal
Affiliation:
Department of Mathematics and Computer Science, Ithaca College, Ithaca, New York 14850
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Abstract

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Let fn be a sequence of nonnegative integers and let f(x): = Σn≥0 fn xn be its generating function. Assume f(x) has the following properties: it has radius of convergence r, 0 < r < 1, with its only singualarity on the circle of convergence at x = r and f(r) = s; y = f(x) satisfies an analytic identity F(x, y) = 0 near (r, s); for some k ≥ 2 F0.j = 0, 0 ≤ j < k, F0.k ≠ 0 where Fi is the value at (r, s) of the ith partial derivative with respect to x and the jth partial derivative with respect to y of F. These assumptions form the basis of what we call the typical and general cases. In both cases we show how to obtain an asymptotic expansion of fn. We apply our technique to produce several terms in the asymptotic expansion of combinatorial sequences for which previously only the first term was known.

Type
Research Article
Copyright
Copyright © Australian Mathematical Society 1994

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