Question 379237
Given a_1 = 2, a_(k+1) = a_k - 4, we have

a_1 = 2
a_2 = a_1 - 4 = 2 - 4 = -2
a_3 = a_2 - 4 = -2 - 4 = -6.

Therefore the common difference is -4, and we can establish:

a_n = 6 - 4n (based on the original conditions)

Also, the Fibonacci sequence is not an arithmetic sequence, as the difference between successive terms increases.