What fact about the cicada demonstrates a pattern observed by scientists?

The life cycle of a cicada is a fact that is observed as a pattern by scientists. 

The life cycle of cicadas range from 2 to 17 years. Scientists observe a pattern of the cicadas appearing after 2 to 17 years. Therefore, this fact was first observed as a pattern by scientists. Similarly, many other patterns are first located, and after further research, the underlying facts and reasons are found.

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