AMC 8 2009 Problem 5
AMC8 2009 年第 5 题
数列与规律★★☆☆☆
A sequence of numbers starts with 1, 2, and 3. The fourth number of the sequence is the sum of the previous three numbers in the sequence: 1+2+3=6. In the same way, every number after the fourth is the sum of the previous three numbers. What is the eighth number in the sequence?
某个数列以 1，2 和 3 开头。第四项是数列里前 3 项之和： 。类似的，第 4 项之后的每一项都是这一项之前的 3 项之和。那么这个数列的第 8 项是多少？
- A.11
- B.20
- C.37
- D.68
- E.99
正确答案 · Correct Answer
D
解析 · Solution
解析整理中
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