Wir betrachten die Wertetabelle

${\displaystyle {}i}$	${\displaystyle {}1}$	${\displaystyle {}2}$	${\displaystyle {}3}$	${\displaystyle {}4}$	${\displaystyle {}5}$	${\displaystyle {}6}$	${\displaystyle {}7}$	${\displaystyle {}8}$
${\displaystyle {}a_{i}}$	${\displaystyle {}2}$	${\displaystyle {}5}$	${\displaystyle {}4}$	${\displaystyle {}-1}$	${\displaystyle {}3}$	${\displaystyle {}5}$	${\displaystyle {}-2}$	${\displaystyle {}2}$

1. Berechne ${\displaystyle {}a_{2}+a_{5}}$.
2. Berechne ${\displaystyle {}\sum _{k=3}^{6}a_{k}}$.
3. Berechne ${\displaystyle {}\prod _{i=0}^{3}a_{2i+1}}$.
4. Berechne ${\displaystyle {}\sum _{i=4}^{5}a_{i}^{2}}$.