MATLAB: How to use sum

Question

I am trying to use sum but with no success!

For example:

n=1:20;
sum(n./2.^n)

or:

n=20;
k=1:n;
sum(k);

but neither works!Am I missing sth here?

Thanks!

Answer 1

%They both work fine

%What is your error message?

%Try

clear sum
n=1:20;
sum(n./2.^n)

Mybe sum is used as a variable in your code