This pattern appears to alternate between doubling and subtracting by 1.
To get from 3 to 6, we multiply by two. To get from 6 to 5, we subtract one. To get from 5 to 10, we multiply by two. To get from 10 to 9, we subtract one. To get from 9 to 18, we multiply by two. To get from 18 to 17, we subtract one.
Therefore, next we need to multiply by two. 17 x 2 = 34 So, the next number is 34.
To find the number after, we subtract one. 34 - 1 = 33 Thus, the number after is 33.
In conclusion, the next two numbers are 34 and 33.
The vector PQ is Q-P = (2, 1). The vector SR is R-S = (2, 2). One is not a multiple of the others, so the vectors are not parallel. In a parallelogram, these vectors would be identical. PQRS is not a parallelogram.