Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Look to the second graph where Wolfram Alpha gives a continuous factorial function:
What is the second graph?
It is not the gamma function, since that has $\Gamma(-1)=0!=1$.
It is a plot of $\Gamma(x+1)$, known to equal $x!$ at integers.
Required, but never shown