#include<cstdio>
#include<algorithm>
#include<cstring>
#include<vector>
using namespace std;
typedef long long ll;
const int mod=1000000007;
inline int add(int a,int b)
{
    a+=b;
    if(a>=mod)a-=mod;
    return a;
}
inline int dec(int a,int b)
{
    a-=b;
    if(a<0)a+=mod;
    return a;
}
inline int mult(int a,int b)
{
    ll t=1ll*a*b;
    if(t>=mod)t%=mod;
    return t;
}
inline int power(int a,int b)
{
    int out=1;
    while(b)
    {
        if(b&1)out=mult(out,a);
        a=mult(a,a);
        b>>=1;
    }
    return out;
}
int T,n,dp[200010][3],cnt[200010],fac[200010],ifac[200010];
bool flag[200010];
inline int C(int a,int b)
{
    if(a<b)return 0;
    return mult(fac[a],mult(ifac[b],ifac[a-b]));
}
int main()
{
    fac[0]=1;
    for(int i=1;i<=200000;i++)fac[i]=mult(fac[i-1],i);
    ifac[200000]=power(fac[200000],mod-2);
    for(int i=199999;i>=0;i--)ifac[i]=mult(ifac[i+1],i+1);
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n);
        fill(cnt,cnt+2*n+1,0);
        fill(flag,flag+2*n+1,0);
        for(int i=1,ti;i<=2*n;i++)
        {
            scanf("%d",&ti);
            cnt[ti]++;
        }
        for(int i=0;i<=2*n;i++)dp[i][0]=dp[i][1]=dp[i][2]=0;
        dp[0][0]=1;
        for(int i=1;i<=2*n;i++)
        {
            if(flag[i-1]==0)
            {
                flag[i]=cnt[i]&1;
                if(flag[i])
                {
                    dp[i][1]=dp[i][2]=mult(dp[i-1][0],C(cnt[i],cnt[i]/2));
                }
                else
                {
                    dp[i][0]=mult(dp[i-1][0],C(cnt[i],cnt[i]/2));
                }
            }
            else
            {
                flag[i]=!(cnt[i]&1);
                if(flag[i])
                {
                    dp[i][1]=add(mult(dp[i-1][1],C(cnt[i],cnt[i]/2)),mult(dp[i-1][2],C(cnt[i],cnt[i]/2-1)));
                    dp[i][2]=add(mult(dp[i-1][2],C(cnt[i],cnt[i]/2)),mult(dp[i-1][1],C(cnt[i],cnt[i]/2-1)));
                }
                else
                {
                    dp[i][0]=mult(add(dp[i-1][1],dp[i-1][2]),C(cnt[i],cnt[i]/2));
                }
            }
        }
        printf("%d\n",dp[2*n][0]);
    }
    return 0;
}