# Homework Help: Finding a recurrence Relation

1. Sep 22, 2012

### Punkyc7

Find a simple closed formula for the ordinary generating function of the sequence given by

{a$_{n}$]}n>=0 when a$_{n}$ is given by

a$_{n}$ = 6 * 5^n - 5 * 3^n.

My question is how do you find the recurrence relation a$_{n}$ = 6 * 5^n - 5 * 3^n.

I don't know were to start.

2. Sep 22, 2012

### gabbagabbahey

Why bother with finding a recurrence relation? Your sequence looks like a combination of two geometric sequences. What is the the generating function for each one? What do you get when you add the two generating functions together?