In your class, you have started lessons about "arithmetic progression". Because you are also a programmer, you have decided to write a function.

This function, arithmetic_sequence_sum(a, r, n), should return the sum of the first (n) elements of a sequence in which each element is the sum of the given integer (a), and a number of occurences of the given integer (r), based on the element's position within the sequence.

For example:

arithmetic_sequence_sum(2, 3, 5) should return 40:

```
1     2        3          4            5
a + (a+r) + (a+r+r) + (a+r+r+r) + (a+r+r+r+r) 
2 + (2+3) + (2+3+3) + (2+3+3+3) + (2+3+3+3+3) = 40
```

Difficulty: introductory

Starter code:

def arithmetic_sequence_sum(a, r, n):
	

Solutions:
def arithmetic_sequence_sum(a, r, n):
    return n * (a + a + ( n - 1) * r) / 2  

def arithmetic_sequence_sum(a, r, n):
    return a * n + r * n * (n - 1) / 2;

def arithmetic_sequence_sum(a, r, n):
    result = 0
    for i in range(n):
        result += a + i*r
    return result

def arithmetic_sequence_sum(a, r, n):
    return sum(a + r*x for x in range(n))


def arithmetic_sequence_sum(a, r, n):
    #Your code here!:)
    return n * (2 * a + (n - 1) * r) / 2

def arithmetic_sequence_sum(a, r, n):
    b=a
    x=n-1
    while x!=0:
        a+=r
        x-=1
    return (n*(b+a))/2

def arithmetic_sequence_sum(a, r, n):
    return int((n / 2) * (2 * a + (n - 1) * r))


def arithmetic_sequence_sum(a, r, n):
    return sum(a+sum(r for _ in range(i)) for i in range(n))

def arithmetic_sequence_sum(a, r, n):
    return (a + r * (n-1) / 2) * n

def arithmetic_sequence_sum(a, r, n):
    return (n / 2) * (2 * a + (n - 1) * r)