Cant figure this formula out.

[wild8900]

So I slept through this chapter in math class (Really I did, when I looked at this pattern I KNEW I remembered it somewhere)
I need to write a experience system formula but to find the exp of the next level. Something like clientr.nextlvl=7+((clientr.level*2)+1);
Obviously thats wrong but its as close as I got...
Heres how I wanted to have it progress as you level:

NPC Code:

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level1 - 7

		+3

level2 - 10

		+5	

level3 - 15

		+7	

level4 - 22

		+9	

level5 - 31

		+11	

level6 - 42

		+13	

level7 - 55

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