* 计算并输出下面级数前n项中（n=50）偶数项的和。

buaa_sheng 和 漠墟小仙 都是正确的.
楼主没说用什么编,
我用VB编一个:

function jishu_2n(Num)
dim sum As Long
dim i As Int
for i=2 to Num
sum = sum + i*(i+1)*(i+2)
i = i + 2
next
jishu_2n = sum
end function

Private Sub Form_Load()
Print (jishu_2n(50))
End Sub

int m; // 每项的乘积
int total = 0;
for (int n = 2; n <= 50; n += 2) // 偶数项
{
m = n * (n + 1) * (n + 2); // 每项的乘积
total += m;
}
cout<<total<<endl; //输出

long f()
{
int i;
long sum;
sum = 0;
for (i=1 ; i<=50 ; i ++)
{
if (i%2 != 0) continue;
sum += i*(i+1)*(i+2);
}
return sum;
}

C语言
main()
{int i;
long s=0;
for(i=1;i<=50;i++)
s=s+i*(i+1)*(i+2);
printf("%ld",s);
}