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ZENODO
Preprint . 2025
License: CC BY
Data sources: ZENODO
ZENODO
Preprint . 2025
License: CC BY
Data sources: Datacite
ZENODO
Preprint . 2025
License: CC BY
Data sources: Datacite
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Moments of the Gamma Distribution Involving Logarithmic Factors

Authors: Dubey, Arya;

Moments of the Gamma Distribution Involving Logarithmic Factors

Abstract

This work presents a unified analysis of the sequence of integrals I_{n,m} = ∫_0^∞ x^n e^{-x} (ln x)^m dx, which are equal to the m-th derivatives of the Gamma function at positive integers, Γ^{(m)}(n+1). The central result expresses the normalized integrals I_{n,m}/n! as a complete Bell polynomial in the polygamma functions (the derivatives of the log-Gamma function). This framework provides a powerful and unified way to generate closed-form expressions, recurrence relations, and exponential generating functions. We explore a combinatorial interpretation, showing these values act as the regularized moments of the number of cycles in a random permutation. The paper also provides a complete asymptotic analysis for large n and discusses the analytic continuation of these integrals into the complex plane. All theoretical results are supported by a fully runnable Python code that uses the mpmath library for high-precision numerical integration and evaluation, serving as a robust verification tool. This paper serves as a definitive expository reference, synthesizing results from special functions, combinatorics, and asymptotic analysis into a single coherent narrative.

Keywords

Bell polynomials, Asymptotic expansions, Random permutations, Special functions, Gamma function, FOS: Mathematics, Fa di Bruno formula, Polygamma function, Mathematics, Stirling numbers

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
0
Average
Average
Average
Green