Question

What is the ${20}^{th}$ term of the sequence defined by $a_n=(n-1)(2-n)(3+n)?$

Answer 1

Finding ${20}^{th}$ term.
Given, $a_n=(n-1)(2-n)(3+n)$
Substituting $n=20$ in $a_n$, we get
$a_{20}=(20-1)(2-20)(3+20)$
$\Rightarrow a_{20}=19\times (-18)\times 23$
$\Rightarrow a_{20}=-7866$

Therefore, the ${20}^{th}$ term of the given sequence is $-7866$.