Find the sum, <i>f</i>(<i>n</i>), of the first n terms of the sequence:
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0, 1, 1, 2, 2, 3, 3........<i>p</i>, <i>p</i>, <i>p</i> +1, <i>p</i> + 1,.....</td></tr></table>
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Go on to prove that <i>f</i>(<i>a</i> + <i>b</i>) &#8722; <i>f</i>(<i>a</i> &#8722; <i>b</i>) = <i>ab</i>, where <i>a</i> and <i>b</i>
are positive integers and 
<i>a</i>  &#x003E;  <i>b</i>.