Chapter 11 - Sequences; Induction; the Binomial Theorem - Section 11.1 Sequences - 11.1 Assess Your Understanding - Page 827: 38

$a_1=1 \\a_2=1 \\ a_3=2 \\ a_4=2 \\ a_5=3$

We are given that $a_n=n -a_{n-1}$ and $a_1=1$. In order to determine the remaining values, we will have to substitute $n=2,3,4,5$ into the given sequence: $a_2=1 -a_1=2-1=1 \\ a_3=3-a_2=3-1 =2 \\ a_4=4-a_3=4-2=2 \\ a_5=5-a_4=5-2=3$