Final answer:
The sequence is generated by the formula a_n = 1 + (-1)^n. To find a_4, plug in the value of n = 4 into the formula: a_4 = 1 + (-1)^4 = 1 + 1 = 2.
Step-by-step explanation:
The sequence is generated by the formula an = 1 + (-1)n. To find a4, plug in the value of n = 4 into the formula:
a4 = 1 + (-1)4
a4 = 1 + (1)4
a4 = 1 + 1
a4 = 2