#include<bits/stdc++.h>

const int MOD = 1e9 + 7;
const int MAXN = 100005;

int a[2 * MAXN], b[2 * MAXN], c[2 * MAXN];
long long fac[2 * MAXN], inv[2 * MAXN];
int n;

int read()
{
    int p = 0;
    char c = getchar();
    while (c < '0' || c > '9') c = getchar();
    while (c >= '0' && c <= '9')
        p = p * 10 + (c - '0'), c = getchar();
    return p;
}

long long power(long long a, long long b)
{
    long long c = 1;
    while(b)
    {
        if (b & 1) c = c * a % MOD;
        a = a * a % MOD;
        b >>= 1;
    }
    return c;
}

long long calc(int x, int y)
{
    return (fac[x] * inv[y] % MOD) * inv[x - y] % MOD;
}

int main()
{
    fac[0] = 1;
    for(int i = 1; i <= 200000; i++) fac[i] = fac[i - 1] * i % MOD;
    inv[200000] = power(fac[200000], MOD - 2);
    for(int i = 199999; i >= 0; i--) inv[i] = inv[i + 1] * (i + 1) % MOD;
    
    int T;
    T = read();
    while(T--)
    {
        n = read();
        for(int i = 1; i <= 2 * n; i++) b[i] = c[i] = 0;
        long long ans = 1;
        for(int i = 1; i <= 2 * n; i++)
        {
            a[i] = read();
            b[a[i]]++, c[a[i]] = i;
            if (i % 2 == 0)
            {
                if (a[i] != a[i - 1]) 
                    ans = ans * 2 % MOD;
                //printf("%d %d\n", i, ans);
            }
        }
        for(int i = 1; i <= 2 * n; i++)
            if (b[i] > 1)
            {
                if (b[i] & 1)
                {
                    ans = ans * calc(b[i], b[i] / 2) % MOD;
                }
                else
                {
                    if (c[i] & 1)
                    {
                        ans = ans * (calc(b[i], b[i] / 2) * inv[2] % MOD + calc(b[i], b[i] / 2 - 1) * inv[2] % MOD) % MOD;
                    }
                    else
                    {
                        ans = ans * calc(b[i], b[i] / 2) % MOD;
                    }
                }
            }
        printf("%d\n", (int)ans);
    }
    return 0;
}