Give the ordinary generating function R(x) for the sequence of numbers r_n which count the number of partitions of the integer n in which parts of only sizes 1, 4, or 9 may occur. Give your answer in closed form, that is a formula that does not include infinite sums or products. (e.g. sigma_i =0^infinity x^n = 1 + x + x^2 + is not in closed form, while 1/1 - x, which is a formula for the same function, is in closed form.)