It's called a linear regression. And your data results in a 'not too accurate' one.

A quartic regression would be better.

Using your data I get a quartic of

This has an R^2 of 1 and that is as good as it gets.

When doing a regression, the closer R^2 is to 1, the better.

A linear regression resulted in about .4. That is bad.

You can do these with Excel or any decent calculator.