Sum of Arithmetic Sequence/Also presented as

Sum of Arithmetic Sequence: Also presented as
The Sum of Arithmetic Sequence can also be seen presented in the forms:

Some present it as:


 * $\ds \sum_{k \mathop = 0}^n \paren {a + k d} = a \paren {n + 1} + \dfrac 1 2 d n \paren {n + 1}$

The reality is that this is a messy result that cannot be presented elegantly.