CA Foundation · Quantitative Aptitude · Sequence and Series
In a sequence, t(1) = 3 and t(n+1) = 2·t(n) − 1 for n ≥ 1. What is the sum of the first four terms?
Generating the terms by the recurrence gives 3, 5, 9 and 17, and these sum to 34.
- A45Correct
- B41
- C49
- D36
Explanation
t(1) = 3, t(2) = 2(3) − 1 = 5, t(3) = 2(5) − 1 = 9, t(4) = 2(9) − 1 = 17. The sum is 3 + 5 + 9 + 17 = 34. So the correct figure is 34, not any listed value.
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