Get product of each pair in an array
<p>I have an array of integers and I have to find product of each pair in array.
Say array is <code>{1,2,3,4}</code> then output should be <code>{1*2, 1*3, 1*4, 2*3, 2*4, 3*4}</code>. </p>

<p>Is there any way other than brute force one to get above result. By brute force I mean take one number from array and loop through the array and store product of each pair. Can this be done in time better than <code>O(n^2)</code>?</p>