Find the first 6 non-zero terms of MacLaurin series of the function erf(x)

Consider the expression ∑_n=1 (-1)ⁿ e^*n/n²

1. Find the symbolic value of this sum.

2. Find an approximation for the value when  = -2.

3. Build a function to calculate an approximation for the value of the given expression for

any value for