How do you make an algebra function for this pattern?

Questions & Answers
1

The pattern goes like this: 1,3,6,10,15,21,28,etc.
Start with 1, add 2, add 3, etc.

I need a function that could find the value given the position in the pattern.
In this example an input of 4 would have an output of 10 since 10 is the value of the 4th position.

Any help on this would be greatly appreciated.

2

This is the function that you are looking for :

nth term = n*(n+1)/2

4th term = 4*(4+1)/2 = 10

-Vatsal