d(4) = 64
substitute n = 2, 3, 4 into d(n) = d(n - 1) + 17
d(2) = d(1) + 17 = 13 + 17 = 30
d(3) = d(2) + 17 = 30 + 17 = 47
d(4) = d(3) + 17 = 47 + 17 = 64
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