Answer
$ a_1=-1 \\ a_2=1 \\ a_3=2 \\ a_4=9 \\ a_5=47$
Work Step by Step
We are given that $a_n=a_{n-2}+n(a_{n-1})$ and $a_1=-1; a_2=1$. In order to determine the remaining values, we will have to substitute $n=3,4,5$ into the given sequence. We use previous terms to compute successive terms as follows:
$ a_3=a_1+3(a_2)=-1+3(1)=2 \\ a_4=a_2+4(a_3)=1+(4)(2)=9 \\ a_5=a_3+5(a_4)=2+5(9)=47$
