The sequence is an geometric progression;
Nth=a₁r^(n-1)
a₁ is the first term=-1
r=ratio=a₂/a₁=6/-1=-6
Nth=-1(-6^(n-1)
NTh=an
a₁=-1(-6⁰)=-1
a₂=-1(-6¹)=6
a₃=-1(-6²)=-36
a₄=-1(-6³)=216
therefore this serie is rising at an increasing fast speed, it is an geometric progression.