        </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> 0 "a+b"            "0"               "0"               "0"             </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> 1 "(1/2)a+(2/3)b"  "(1/2)a+(1/6)b"   "(1/6)b"          "0"             </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> 2 "(1/5)a+(2/5)b"  "(3/5)a+(4/15)b"  "(1/5)a+(4/15)b"  "(1/15)b"       </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> 3 "(1/20)a+(1/5)b" "(9/20)a+(3/10)b" "(