Which of these is NOT a geometric sequence?
1,2,4,81, 2, 4, 81,2,4,8
1,3,9,271, 3, 9, 271,3,9,27
1,2,3,41, 2, 3, 41,2,3,4
1,−1,1,−11, -1, 1, -11,−1,1,−1