Add all elements with each other in array in O(n) time

Question

Suppose an array consist of 3 elements:

 A=[1,2,3]

What I want to know is that, is it possible to add each element of array with each other such that time complexity is O(n)?. Result should have

b=[(1+1),(1+2),(1+3),(2+2),(2+3),(3+3)]

Answer 1

No, that's O(n^2).

Now let's see someone prove me wrong ... even better, someone has proven my assertion right -- see the comments below.