As you can see, the sequence starts at -10 and increases by 7 units each time. So, one possible sequence is:
an=7n-17
Let's verify it:
a1=7(1)-17=7-17=-10
a2=7(2)-17=14-17=-3
a3=7(3)-17=21-17=4
a4=7(4)-17=28-17=11
Therefore the next item in the sequence is:
a5=7(5)-17=35-17=18