Sweet potato casserole

3 cups cooked sweet potatoes 1 cup sugar 1.5 tsp vanilla 2 eggs 1/2 c. butter (melted) pour into greased casserole pan top with following mixture: 1.5 cups chopped pecans 1/2 c butter 1/2 cup brown sugar 1/4 c flour cook about 35 mins. at 350 degrees