What is the sum of the first 100 positive integers? The formula for the sum of integers $$1$$ through $$n$$ is $$n(n+1)/2$$. Define $$n=100$$ and then use R to compute the sum of $$1$$ through $$100$$ using the formula. What is the sum?

### Example

With the code below you can compute the sum for the first 20 integers. You can copy and past the code in the R console to evaluate that the code.

20*(20+1)/2


However, we can also define a variable n to re-use the formula for other values of n

• We first define the variable n and set it equal to 20
• Next we calculate the formula
n <- 20
n*(n+1)/2


We can reuse the same code and redefine n so to repeat the calculation for n=25.

n <- 25
n*(n+1)/2


### Exercise

Now, adjust the code from the example to calculate the sum of the first 100 integers.