n=1~0; n=2~2; n=3 ~2,; n=4 ~6; n=5 ~10;看规律,n为偶数则前一项乗2再加2,否则减2
#include<stdio.h>
int main()
{
int n,f[1002],i;
f[1]=0;
for(i=2;i<=1000;i++)
if(i%2==0)
f[i]=(f[i-1]*2+2)000;
else
f[i]=(f[i-1]*2-2)000;
while(scanf("%d",&n)==1&&n)
{
printf("%dn",f[n]);
}
return 0;
}