Chapter 14 - Sequences, Series, and the Binomial Theorem - 14.1 Sequences and Series - 14.1 Exercise Set - Page 894: 26

$a_{1}=(1)^2-2(1)=1-2=-1$ $a_{2}=(2)^2-2(2)=4-4=0$ $a_{3}=(3)^2-2(3)=9-6=3$ $a_{4}=(4)^2-2(4)=16-8=8$ $a_{10}=(10)^2-2(10)=100-20=80$ $a_{15}=(15)^2-2(15)=225-30=195$

If we want to find a term, we have to substitute $n$ by its index: $a_{1}=(1)^2-2(1)=1-2=-1$ $a_{2}=(2)^2-2(2)=4-4=0$ $a_{3}=(3)^2-2(3)=9-6=3$ $a_{4}=(4)^2-2(4)=16-8=8$ $a_{10}=(10)^2-2(10)=100-20=80$ $a_{15}=(15)^2-2(15)=225-30=195$