4, 6, 10, 14, 22, 26, 34, 38, 46, 50
This serie is developed as follows: 4 + 2 = 6 6 + 4 = 10 10+ 4 = 14 14+ 8 = 22 22+4 = 26 26+ 8= 34 34+4 = 38 38+8 = 46 46+? = ? , 46+4 = 50 The solution is 50