# How do I find a formula for #s_n# for the sequence -2, 1, 6, 13, 22,...?

##### 1 Answer

Jan 28, 2015

I would suggest you to find the formula for

The idea is that the differences have been increasing by 2.

-2 to 1 is +3

1 to 6 is +5

6 to 13 is +7

So

One can guess that

For

Good luck!