Question: I am trying to integrate a version/source control system with my unity project. [This answer](http://answers.unity3d.com/answers/1251608/view.html) directed me towards using source/version control. (I dont know the difference.) 

The answer links to a tutorial which explains creating the repository and pushing it to a remote service. I followed the whole tutorial. But I still don't understand how this integrates with my current projects.

My question is that.

1. how can I do this locally
2. how will this make it possible to revert to previously-saved versions?

Answer: 
This is simple math, the php code does exactly what it looks like it does. Am I missing something?

loop 1: 

```
    $i = 1
    $s = 0 + (2*1 + 5) = 7

```

loop 2: 

```
    $i = 2
    $s = 7 + (2*2 + 5) = 7 + 4 + 5 = 16

```

loop 3: 

```
    $i = 3
    $s = 16 + (2*3 + 5) = 16 + 6 + 5 = 27

```

loop 4: 

```
    $i = 4
    $s = 27 + (2*4 + 5) = 27 + 8 + 5 = 40

```
This is simple math. s is the sum of for i from 1 to n+2 of 2i+a. This is equal to the twice sum of i plus the sum of a. The latter is clearly worth (n+2)a. The former is twice the sum of integers from 1 to n+2, i.e. 2 \* (n+2)(n+3)/2. The total is thus (n+2)(n+3) + (n+2)a = (n+2)(n+3+a) = (2+2)\*(2+3+5) = 4\*10 = 40. (Side effect: no need to have an explicit loop, just implement the above formula.)