This is a geometric sequence because dividing any term by the previous term results in a constant called the common ratio. Any geometric sequence can be expressed as:
a(n)=ar^(n-1), a=initial term, r=common ratio, n=term number.
The common ratio,r, is -16/8=32/-16=-64/32=-2, and the first term, a, is 8
So the rule for this sequence is:
a(n)=8(-2)^(n-1), so the 13th term is:
a(13)=8(-2^12)
a(13)=32768
