If we make one rod a known and designated white rod, then the remaining white rod can exist in 8 different positions, meaning that for each fixed white rod, there are 8 variations of the second white rod
This means there are 9*8 = 72 possible configurations if both white rods are treated discretely. However as i assume each white rod is interchangeable for the sake of patterns, then for each of the configurations of fixed white rod and non-fixed white rod, there is an opposite case of the same pattern appearing with a non fixed white rod and a fixed white rod. This means you divide 72 in half, to get 36.
The answer is therefore 36