I'd like to assess the following expression:
1-2+5-...+-(2^n - n)
which should be presented as a "Sum".
Now I thought about defining this expression:
it's MINUS for n = straight number
it's PLUS for n = odd number
n= 3 -> +(2^3 - 2) = +5
n=2 -> - (2^2 - 2) = -2
How can I do this? Or is there a simplier way?