4, 12, 20
Series would be: 4 + 8 * (n - 1) = 4 + 8n - 8 = 8n - 4
n = 1 ==> 4
n = 2 ==> 12
n = 3 ==> 20
n = 41 ==> 4 + 8 *(41 -1) = 4 + 8 * 40 = 4 + 320 = 324
Answer:
324
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