not guaranteed. may times I have experienced that berth no 65 68 as SS qouta seats in most of coaches of train leaving from LTT.
As per your query seems difficult to get 3 in row. If 15 seats are avl, I suggest that wait for it to become RAC and then book. chances are very high of getting 3 seats in a row. but keep checking regularly should be the least possible RAC . better less than 10