List the next three terms in the following sequence:1, 2, 4, 7, 11, 16,...Also list the number that would be the twentieth number in the sequence.

The differences between consecutive terms are 1, 2, 3, 4, and 5, so continue by adding 6, 7, and 8. This gives the next three terms 22, 29, and 37. The 20th term is 1 plus the sum of the first 19 positive integers: 1 + (19 × 20 ÷ 2) = 191. Choice D lists these terms and the 20th term.

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