Question

Here are the first four terms of a number sequence.

2, 5, 11, 23

The rule to continue this sequence is multiply the previous term by 2 and then add 1.

Work out the 5th term of this sequence.

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Answer 1

47

Explanation:

The rule to get the next number in the sequence is multiply the current term by 2 and add 1

Fourth term is 23

Fifth term is 2 · 23 + 1 = 46 + 1 = 47

For this sequence, the nth term is
aₙ = 2aₙ₋₁ + 1 with a₁ = 2