Asymptotic behavior of this function?

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Discussion Overview

The discussion focuses on estimating the asymptotic behavior of the function f(x) = ∑_{k=1}^{x} log(k). Participants seek a closed form function g(x) such that the ratio f(x)/g(x) approaches 1 as x approaches infinity. The conversation includes references to established approximations and methods.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant asks how to estimate the asymptotic behavior of the function f(x) = ∑_{k=1}^{x} log(k).
  • Another participant confirms that f(x) can be expressed as log(x!) and suggests using Stirling's approximation as a standard asymptotic approximation for the factorial function.
  • A later reply mentions the Euler–Maclaurin formula as providing good approximations, noting that it includes a particular case that gives Stirling's approximation.

Areas of Agreement / Disagreement

Participants generally agree on the use of Stirling's approximation for estimating the asymptotic behavior, but the discussion includes references to alternative methods without resolving which is preferable.

Contextual Notes

The discussion does not clarify specific assumptions or limitations regarding the application of Stirling's approximation or the Euler–Maclaurin formula in this context.

asmani
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Hi

How to estimate the asymptotic behavior of this function?

f(x)=\sum_{k=1}^{x}\log(k)
I mean, a closed form function g(x) such that f(x)/g(x) tends to 1 as x goes to infinity.
 
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asmani said:
Hi

How to estimate the asymptotic behavior of this function?

f(x)=\sum_{k=1}^{x}\log(k)
I mean, a closed form function g(x) such that f(x)/g(x) tends to 1 as x goes to infinity.

x is an integer, yes? Then f(x) = \log(x!). The standard asymptotic approximation for the factorial function is Stirling's approximation.
 
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Haha, exactly what I was looking for. Thanks!
 

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