<body>
<input type="text" id="abc" />
<input type="button" value="阶乘求和结果" onclick="a()" />
</body>
</html>
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function a()
{
var n=document.getElementById("abc");
var n1=n.value;
var c=isNaN(n1);
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for (var i = 1; i <= n1; i++)
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{
sum1 *= j;
}
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document.writeln(sum);
}
else
{
alert("你的输入有误！");}
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{
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if(i % 7 == 0 || i % 10 == 7||i/10>=7&&i/10<8)
{
document.writeln(i);
sum+=i;
}
}
document.writeln(sum);
}
b();
</script>
