Answer
$a_{n}=n-4, \quad n=1,2,3...$
Work Step by Step
The differences between the terms are $1,1,1,1,...$
This is constant, just like the sequence of natural numbers:
$1,2,3,4,....$
We find a relationship by observing the pattern:
$-3=1-4\quad$ = $n-4$ when $n=1,$
$-2=2-4\quad$ = $n-4$ when $n=2,$
$-1=3-4\quad$ = $n-4$ when $n=3,$
$ 0=4-4\quad$ = $n-4$ when $n=4$
$ 1=5-4\quad$ = $n-4$ when $n=5$
$...$
$a_{n}=n-4, \quad n=1,2,3...$
