Create a program using the for$-$end loop to calculate the first $20$ terms of the equation $($use an input command to enter $\text{'}x\text{'})$:

$e^x={\displaystyle \underset{n=0}{\overset{}{}}}\frac{1}{n!}{x}^n$

Test the program for several values of $x($for example, $1,2\mathrm{.}5,6).$