Share a pen question [How many parts a plane can be divided into with n straight lines] _ javascript tips-js tutorial

Today, I chatted with a colleague on the subway and gave me a question. I came back and thought about what I wrote, I used the knowledge of digital reasoning in the field test. Of course, this can be written recursively, and my code and recursive ideas can be discussed. The Code is as follows:

Question:

How many parts can a plane be divided into at most n straight lines?


Number of lines:

Inner point:

Split count: