[Math] Alternative definition of Gamma function

gamma function

The Gamma function is defined in terms of an integral as

The notation $Γ(t)$ is due to Legendre. If the real part of the complex number $t$ is positive $(Re(t) > 0)$, then the integral
$$
\Gamma(t) = \int_0^\infty x^t e^{-x}\,\frac{{\rm d}x}{x}
$$
converges absolutely, and is known as the Euler integral of the second kind (the Euler integral of the first kind defines the Beta function).

Can it be equivalently defined in terms of a recursive relation as
$$ \Gamma(t+1)=t \Gamma(t)$$ $$\Gamma(1)=1$$
with some non-redundant conditions?

Thanks!

Best Answer

Baby Rudin gives the following definition:

$\forall x\in(0,+\infty):\ \Gamma(x+1)=x\Gamma(x);$

$\forall n\in{\Bbb N}:\ \Gamma(n+1)=n!;$

$\log\Gamma$ is convex in $(0,+\infty)$.

Related Question