Two patterns alternate here, with every third number following the alternate pattern. In the main series(1st series) 4, 7, 10,13, 16 ..... beginning with 4, 3 is added to each number to arrive at the next. Secondary series (2nd series): 26, 20, ... beginning with 26, 6 is subtracted from each number to arrive at the next. Therefore Next two number is 19(from 1st series), 14(from 2nd series). 19,14