Question

Look at this sequence of numbers: 0, 1, 2, 4, 6, 9, 12, 16, ? - what number should replace the question mark?

Answer 1

20

Explanation:

0 to 1 = a difference of 1

1 to 2 = a difference of 2-1 = 1

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2 to 4 = a difference of 2

4 to 6 = a difference of 2

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6 to 9 = a difference of 3

9 to 12 = a difference of 3

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12 to 16 = a difference of 4

16 to 20 = a difference of 4