Respuesta :

1 to 2
Multiply by 2

2 to 3
Add by 1

3 to 6
Multiply by 2

6 to 7
Add by 1

7 to 14
Multiply by 2

14 to 15
Add by 1

Do you see the pattern?

Multiply by 2 and then add by 1; repeat the process.

Have an awesome day! :)