12, 17, 38, 117, ?, 2351
a) 470
b) 490
c) 510
d) 540
e) 450
Sol:
12 * 1 + 5 = 17
17 * 2 + 4 = 38
38 * 3 + 3 = 117
117 * 4 + 2 = 470
470 * 5 + 1 = 2351
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