求助！！！用VF, do while 求等差数列和

求助！！！用VF, do while 求等差数列和

i的初始值应该是4 s的初始值应该是0
程序如下：

SET TALK OFF
i=4
s=0
DO WHILE i<=14
s=s+i
i=i+2
ENDDO
? "和是：",s
SET TALK ON

&lt;html&gt; &lt;body&gt; &lt;form action="" method="post"&gt; &lt;% string strstep = request.getparameter("step"); int step = 0; if (strstep != null && strstep.trim().length() != 0) { step = integer.parseint(strstep); } else { strstep = ""; } %&gt; &lt;table&gt; &lt;tr&gt; &lt;td&gt; 请输入等差数列的步长：&lt;input type="text" name="step" value="&lt;%=strstep%&gt;"/&gt; &lt;/td&gt; &lt;td&gt;&lt;input type="submit" value="确 定"/&gt;&lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;% if (step != 0) {%&gt; &lt;br/&gt; &lt;div&gt; 等差数列结果: &lt;br/&gt; &lt;% int curnum = 1; int linenum = 1; do { if (curnum &lt; 10) { out.print("&nbsp;" + curnum + "&nbsp;"); } else { out.print(curnum + "&nbsp;"); } linenum ++; if (linenum == 10) { out.print("&lt;br/&gt;"); linenum = 1; } curnum += step; } while (curnum &lt;= 90); %&gt; &lt;/div&gt; &lt;%}%&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt;