51Nod 1228 -- 伯努利数

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 #include<cmath>
 5 using namespace std;
 6 #define M 1000000007
 7 #define K 2010
 8 #define ll long long
 9 int T,i;
10 ll k,m,inv[K],n,j,c[K][K],b[K],Ans;
11 int main()
12 {
13     for(inv[1]=1,i=2;i<K;i++)inv[i]=(M-M/i)*inv[M%i]%M;
14     for(i=1;i<K;i++){
15         c[i][0]=c[i][i]=1;
16         for(j=1;j<i;j++)
17         c[i][j]=(c[i-1][j]+c[i-1][j-1])%M;
18     }
19     for(b[0]=1,i=1;i<K-1;i++){
20         for(j=0;j<i;j++)b[i]=(b[i]-b[j]*c[i+1][j])%M;
21         b[i]=(b[i]*inv[i+1])%M;
22     }
23     scanf("%d",&T);
24     while(T--){
25         scanf("%I64d%d",&n,&k);
26         Ans=0;n%=M;
27         for(i=1,j=n+1;i<=k+1;i++,j=(j*(n+1))%M)Ans=(Ans+(c[k+1][i]*b[k-i+1]%M)*j%M)%M;
28         Ans=(Ans*inv[k+1])%M;
29         printf("%I64d\n",(Ans+M)%M);
30     }
31     return 0;
32 }