Rastas's has been given a number n. Being weak at mathematics, she has to consider all the numbers from 1 to 2n - 1 so as to become perfect in calculations. (You can assume each number is consider as a soldier).
We define the strength of number i as the number of set bits (bits equal to 1) in binary representation of number i.
If the greatest common divisor of numbers a and b is gcd(a, b),
Rastas would like to calculate the function S which is equal to:
As the friend of Rastas, it's your duty to calculate S modulo 109 + 7.
Input
The first line of the input contains the number of test cases, T. Each of the next T lines contains an integer n, as mentioned in the question
Output
For each value of n given, find the value of the function S.
Constraints
Sum of n over all test cases doesn't exceed 2500.
Example
Input: 3
1
2
5
Output:
0
3
680
The meaning of the question: Given N, find ,
That is, for these (i, j), i and j are expressed in binary, and the gcd of the number of 1s in the binary of i and j is accumulated.
Idea: Considering that 2^N-1 is very large, it is directly considered for binary, because there are at most 2500 1s, and O(N^2) can be done violently. We consider the number of combinations, enumerating (i,j) with X 1s and Y 1s, and the contribution is nun[X]*num[Y]*gcd(X,Y). When X equals Y, subtract yourself. Where num[X]=C(X,N);
#include<bits/stdc++.h> #define ll long long using namespace std; const int Mod=1e9+7; int c[2510],fac[2510]; int qpow(int a,int x){ a%=Mod; int res=1; while(x){ if(x&1) res=(ll)res*a%Mod; a=(ll)a*a%Mod; x>>=1; } return res; } int gcd(int a,int b){ if(b==0) return a; return gcd(b,a%b); } intmain () { int N,M,i,j,T,ans; fac[0]=1; for(i=1;i<=2500;i++) fac[i]=(ll)fac[i-1]*i%Mod; scanf("%d",&T); while(T--){ ans=0; scanf("%d",&N); for(i=1;i<=N;i++){ c [i] = (ll) fac [N] * qpow (fac [i], Mod- 2 )% Mod * qpow (fac [Ni], Mod- 2 )% Mod; } for(i=1;i<=N;i++) { for(j=1;j<=N;j++){ if(i!=j) ans=(ans+(ll)c[i]*c[j]%Mod*gcd(i,j))%Mod; else ans=(ans+(ll)c[i]*(c[i]-1)%Mod*i)%Mod; } } ans = (ll) ans * qpow ( 2 , Mod- 2 )% Mod; printf("%d\n",ans);// } return 0; }