Let a be the first term and d be the common difference.
Now, a3=-13
=> a + 2d = -13 ---------(1)
now, a6 = 2
=> a + 5d = 2 -----------(2)
Subtracting (1) from (2) we get
5d-2d = 2+13
3d = 15
d = 5
Now, from equation (1) we get
a = -13 - 2x5 = -23
The required A.P is given by
a, a+d, a+2d, ...........
So, A.P is -23, -18, -13, -8, -3, 2,......