#### Answer

$a_{1}=5$
$a_{2}=25$
$a_{3}=125$
$a_{4}=625$
$a_{100}=5^{100}\approx 7.89\times 10^{69}$

#### Work Step by Step

We are given:
$a_{n}=5^{n}$
We evaluate:
$a_{1}=5^{1}=5$
$a_{2}=5^{2}=25$
$a_{3}=5^{3}=125$
$a_{4}=5^{4}=625$
$a_{100}=5^{100}\approx 7.89\times 10^{69}$