Do we have a general solution infinite series for the gamma function?

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Discussion Overview

The discussion revolves around the existence of a general infinite series solution for the gamma function, specifically whether such a representation can be expressed in the form of a summation involving a function of \( n \) and \( k \). The scope includes theoretical exploration of the gamma function and its properties.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the existence of an infinite series summation for the gamma function, suggesting forms such as \( \frac{1}{\Gamma(k)}=\sum_{n=0}^{\infty} f(n,k) \) or \( {\Gamma(k)}=\sum_{n=0}^{\infty} f(n,k) \).
  • Another participant references Wikipedia, noting two general solutions involving Laguerre polynomials and a series expansion around \( z=1 \), questioning the restrictions these may impose on the function's input.
  • One participant asserts that \( \frac{1}{\Gamma} \) is an entire function and mentions that its Taylor series converges everywhere, suggesting that the coefficients are detailed in the Wikipedia article on the reciprocal gamma function.
  • There is a suggestion that the Taylor series might be considered another general solution for \( \frac{1}{\Gamma} \).
  • A later reply indicates an update to a function that now also accommodates imaginary values, expanding its applicability.

Areas of Agreement / Disagreement

Participants express varying viewpoints on the existence and forms of infinite series solutions for the gamma function, with no consensus reached on a definitive general solution. Some participants propose specific forms while others question their limitations.

Contextual Notes

There are mentions of restrictions related to the use of Laguerre polynomials and the convergence of series expansions, particularly concerning the absolute value of \( z-1 \). The discussion does not resolve these limitations.

mesa
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Does anyone know if we currently have an infinite series summation general solution for the gamma function such as,


$$\frac{1}{\Gamma(k)}=\sum_{n=0}^{\infty} f(n,k)$$

or,

$${\Gamma(k)}=\sum_{n=0}^{\infty} f(n,k)$$?
 
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mathman said:

How I miss these things in wikipedia I will never know...
Okay I see the following two general solutions,

$$\Gamma(t)=x^t \sum_{n=0}^{\infty} \frac{L_n^{(t)}(x)}{t+n}$$

$$\Gamma(z) = 1+\sum_{k=1}^\infty\frac{\Gamma^{(k)}(1)}{k!}(z-1)^{k}$$

For the first one I am unfamiliar with Laguerre polynomials. Does this cause any restrictions on the input of the function?

The second one only works for the absolute value of (z-1)<1 so it is pretty limited.

Are there any others?
 
Well I have something much better, if anyone knows of anything else please respond.
 
1/\Gamma is an entire function, so its Taylor series converges to it everywhere. The coefficients are given at Wikipedia's article on the reciprocal gamma function.
 
eigenperson said:
1/\Gamma is an entire function, so its Taylor series converges to it everywhere. The coefficients are given at Wikipedia's article on the reciprocal gamma function.

Are you referring to the Taylor series as another general solution except in the form of 1/\Gamma?
 
Update, my function now also works for imaginary values in addition to the real number line.
 

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