What is the $20^{\text {th }}$ term of the sequence defined by
$a_{n}=(n-1)(2-n)(3+n) ?$
What is the $20^{\text {th }}$ term of the sequence defined by
$a_{n}=(n-1)(2-n)(3+n) ?$
Putting $n=20,$ we obtain
$a_{20} =(20-1)(2-20)(3+20) $
$=19 \times(-18) \times(23)=-7866$
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