15. 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 4 experience points.
On level 3, a player must earn 8 experience points.
On level 4, a player must earn 13 experience points.
Which recursive equation represents the pattern? (2 points)
Oan = an - 1 +n
O an = an - 1 + (n + 1)
O a, = an- 1 + 2n
O a, = a,- 1 + (2n + 1)