What is the rest of the pattern for 5 15 45 135?

Answer 1

There are many possible answers.

The simplest polynomial solution is

Un = (20n3 - 90n2 + 160n - 75)/3 for n = 1 , 2, 3, ... and accordingly, the next few terms are 325, 655, 1165, etc.

An alternative is a geometric sequence of the form

Vn = 5*3n-1 where n = 1, 2, 3, ...

so the next few terms will be 405, 1215, 3645, etc.