The Ramanujan Journal

, 20:179

On an asymptotic series of Ramanujan

Open AccessArticle

DOI: 10.1007/s11139-009-9169-x

Cite this article as:
Yu, Y. Ramanujan J (2009) 20: 179. doi:10.1007/s11139-009-9169-x


An asymptotic series in Ramanujan’s second notebook (Entry 10, Chap. 3) is concerned with the behavior of the expected value of φ(X) for large λ where X is a Poisson random variable with mean λ and φ is a function satisfying certain growth conditions. We generalize this by studying the asymptotics of the expected value of φ(X) when the distribution of X belongs to a suitable family indexed by a convolution parameter. Examples include the binomial, negative binomial, and gamma families. Some formulas associated with the negative binomial appear new.


Asymptotic expansionBinomial distributionCentral momentsCumulantsGamma distributionNegative binomial distributionPoisson distributionRamanujan’s notebooks

Mathematics Subject Classification (2000)

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© The Author(s) 2009

Authors and Affiliations

  1. 1.Department of StatisticsUniversity of CaliforniaIrvineUSA