Multiple choice

Find the wrong number in the following number series. $2, 13, 65, 271, 817, 1639, 1645$

  1. 13

  2. 65

  3. 271

  4. 817

  5. 1639
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B Correct answer
Explanation

Pattern: differences are 11, 52, 206, 546, 822. These don't show clear pattern. Try: 4³-3=61 (not 65), 5³+46=171 (not 271). Another pattern: 2×6+1=13, 13×5=65, 65×4+1=261 (not 271). 65 may not be wrong. Let me check: 2, 13, 261, 813, 1639 would follow ×6.5, ×20, ×6.5 pattern. 65 seems incorrect.

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