Larry and Jeff are in a flower shop containing an infinite number of roses and tulips and no other type of flower. They are both buying bouquets. Both bouquets must contain at least six flowers. Additionally, Larry would like his to contain an even number of roses, but no tulips. Find the generating function for the number of ways to choose both bouquets such that the overall number of flowers in the bouquets is equal to n. Use this to calculate the number of ways to choose the bouquets in such a way that the total number of flowers is equal to 17.