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 1 experience point.
On level 2, a player must earn 6 experience points.
On level 3, a player must earn 13 experience points.
On level 4, a player must earn 22 experience points.
How many experience points must a player earn on level 7?