A video game has been developed whereby the player must earn a certain number of experience points before progressing to the next level.
On level 1, a player must earn 2 experience points. On level 2, a player must earn 4 experience points. On level 3, a player must earn 7 experience points. On level 4, a player must earn 11 experience points.
How many experience points must a player earn on level 7?