#include<stdio.h>
#include<stdlib.h>
#include<algorithm>
#include<math.h>
#include<string.h>
#include<string>
#include<time.h>
#include<stack>
#include<map>
#include<set>
#include<queue>
#include<unordered_map>
#include<ctype.h>
#include<random>
#include<iostream>
#include<bitset>
using namespace std;
typedef long long ll;
typedef long long LL;
typedef double db;
#define _Zero(a) memset(a,0,sizeof(a))
#define _Neg1(a) memset(a,-1,sizeof(a))
#define _Inf(a) memset(a,0x3f,sizeof(a))
#define _NegInf(a) memset(a,0xcf,sizeof(a))
#define _Rep(i,a,b) for(int (i)=(a);(i)<=(b);i++)
#define _Dep(i,a,b) for(int (i)=(a);(i)>=(b);i--)
#define _Out(a)    cerr<<(#a)<<" = "<<(a)<<endl
const int INF = 0x3f3f3f3f;
const int MAXN = 2e5 + 50;
const ll LINF = 0x3f3f3f3f3f3f3f3f;
const ll MOD = 1e9 + 7;
const db EPS = 1e-6;
const db Pi = acos(-1);
void test() { cerr << "\n"; }
template <typename T,typename...Args>void test(T x,Args...args){cerr<<x<<" ";test(args...); }
ll qpow(ll a, ll b) {return b?((b&1)?a*qpow(a*a%MOD,b>>1)%MOD : qpow(a*a%MOD,b>>1))%MOD :1; }
ll qpow(ll a, ll b, ll c) {return b?((b&1)?a*qpow(a*a%c,b>>1)%c : qpow(a*a%c,b>>1)) % c: 1; }
ll gcd(ll a, ll b){return b?gcd(b,a% b): a; }
int sign(db x) { return x<-EPS ? -1: x>EPS; }
int dbcmp(db l, db r) { return sign(l - r); }

const ll mod=1e9+7;
const int N=1e6+10;
ll fac[N],inv_fac[N];

long long jc[1000000],ny[1000000];  //jc[i]表示i的阶乘   ny[i]表示i的阶乘的逆元
long long C(long long n,long long m)  //求组合数
{
    swap(n,m);
    if(n==0||n==m)return 1;
    return jc[m]*ny[n]%mod*ny[m-n]%mod;  //m的阶乘*n阶乘的逆元*（m-n）阶乘的逆元
}

int cnt[MAXN];
ll dp[3];
int main()
{
    int T;
    jc[1]=1;
    ny[1]=1;
    for(int i=2;i<400050;i++) //预处理jc数组和ny数组
    {
     jc[i]=jc[i-1]*i%mod;
     ny[i]=qpow(jc[i],mod-2);
    }
   // printf("%lld\n",C(5,2));
    scanf("%d",&T);
    while(T--)
    {
        int n;
        scanf("%d",&n);
        for(int i=1;i<=n*2;i++)cnt[i]=0;
        for(int i=1;i<=n*2;i++)
        {
            int x;
            scanf("%d",&x);
            cnt[x]++;
        }
        int la=0;dp[0]=1;dp[1]=dp[2]=0;
        for(int i=1;i<=2*n;i++)
        {
            ll tmp[3]={0};
           // printf("%d:%lld %lld ",i,dp[1],dp[2]);printf("%lld\n",dp[0]);printf("%d\n",cnt[i]);
            if(cnt[i]==0)continue;
            if(cnt[i]%2)
            {
                tmp[0]=(tmp[0]+(dp[1]+dp[2])*C(cnt[i],cnt[i]/2+1))%mod;
                tmp[1]=(tmp[1]+dp[0]*C(cnt[i],cnt[i]/2+1))%mod;
                tmp[2]=(tmp[2]+dp[0]*C(cnt[i],cnt[i]/2+1))%mod;
            }
            else
            {
                tmp[0]=(tmp[0]+dp[0]*C(cnt[i],cnt[i]/2))%mod;
                tmp[1]=(tmp[1]+dp[1]*C(cnt[i],cnt[i]/2))%mod;
                tmp[2]=(tmp[2]+dp[2]*C(cnt[i],cnt[i]/2))%mod;
                tmp[1]=(tmp[1]+dp[2]*C(cnt[i],cnt[i]/2+1))%mod;
                tmp[2]=(tmp[2]+dp[1]*C(cnt[i],cnt[i]/2+1))%mod;
            }
            dp[0]=tmp[0];dp[1]=tmp[1];dp[2]=tmp[2];
        }

       // printf("%lld %lld ",dp[1],dp[2]);
        printf("%lld\n",dp[0]);
    }
}
/*

*/