Question
Select the number from among the given options that can
replace the question mark (?) in the following series. 4, 21, 85, 256, 513, ?Solution
4 × 5 + 1 = 21 21 × 4 + 1 = 85 85 × 3 + 1 = 256 256 × 2 + 1 = 513 513 × 1 + 1 = 514
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