Answer
$a_1=1$
$a_2=\frac{1}{2}$
$a_3=\frac{1}{6}$
$a_4=\frac{1}{24}$
Work Step by Step
We know that $a_n=\frac{1}{n!}$. Hence, here:
$a_1=\frac{1}{1!}=\frac{1}{1}=1$
$a_2=\frac{1}{2!}=\frac{1}{2}$
$a_3=\frac{1}{3!}=\frac{1}{6}$
$a_4=\frac{1}{4!}=\frac{1}{24}$