## Precalculus (6th Edition) Blitzer

$95$
In order to calculate the first $4$ terms of the sequence we will have to plug $n=1,2,3,4$ into the given equation. So, we get $a_1=-1,a_2=5, a_3=15; a_4=29; a_5=47$ Thus, we have the sum $=-1+5+15+29+47=95$