Question 889172
2,4,7,12,21,...
<pre>
Take 2
Add 1, get 3
Multiply by 2, get 6
Subtract 2, get 4.

Take 4
Add 1, get 5
Multiply by 2, get 10
Subtract 3, get 7.

Take 7
Add 1, get 8
Multiply by 2, get 16
Subtract 4, get 12

Take 12
Add 1, get 13
Multiply by 2, get 26
Subtract 5, get 21

Take 21
Add 1, get 22
Multiply by 2, get 44
Subtract 6, get 38

Edwin</pre>