hdu 2042

题意：（略）太长了

解法：找规律，发现A[i]=A[i-1]*2-2;

   1:  #include<stdlib.h>
   2:  #include<string.h>
   3:  #include<stdio.h>
   4:  #include<math.h>
   5:  #define N 31
   6:  int a[N]={3};
   7:  void init(){
   8:      int i;
   9:      for(i=1;i<N;i++){
  10:          a[i]=a[i-1]*2-2;//这个就是递推式
  11:      }
  12:  }
  13:  int main(){
  14:      int n,i;
  15:      init();
  16:      while(scanf("%d",&n)!=EOF){
  17:          while(n--){
  18:              int tmp;
  19:              scanf("%d",&tmp);
  20:              printf("%d
",a[tmp]);
  21:          }
  22:      }
  23:  }