Quantitative reasoning Practice Test

Give the missing term in the sequence:

$\left \{ 1 \right \}$

$\left \{ 1,2 \right \}$

$\left \{ 1,3 \right \}$

$\left \{ 1,2,4 \right \}$

$\left \{ 1,5\right \}$

$\left \{ 1,2, 3 , 6 \right \}$

$\left \{ 1,2,4, 8 \right \}$