#include <cstdio>

const int M = 1000000007;
const int _n = 200000 + 10;
int T;
int n;
int c[_n];
int up[_n], down[_n];
int now;
int f[_n][2];

int C(int n, int m)
{
    if (n < m)
    {
        return 0;
    }
    return (long long)up[n] * down[m] % M * down[n - m] % M;
}

int main()
{
    up[0] = 1;
    for (int i = 1; i <= 200000; i++)
    {
        up[i] = (long long)up[i - 1] * i % M;
    }
    down[0] = down[1] = 1;
    for (int i = 2; i <= 200000; i++)
    {
        down[i] = (long long)(M - M / i) * down[M % i] % M;
    }
    for (int i = 2; i <= 200000; i++)
    {
        down[i] = (long long)down[i - 1] * down[i] % M;
    }
    scanf("%d", &T);
    while (T--)
    {
        scanf("%d", &n);
        n = n * 2;
        for (int i = 1; i <= n; i++)
        {
            c[i] = 0;
            f[i][0] = f[i][1] = 0;
        }
        for (int i = 1; i <= n; i++)
        {
            int x;
            scanf("%d", &x);
            c[x]++;
        }
        now = 0;
        f[0][0] = 1;
        for (int i = 1; i <= n; i++)
        {
            int x = now;
            now += c[i];
            f[i][0] = ((long long)f[i - 1][0] * C(c[i], now / 2 - x / 2) % M + (long long)f[i - 1][1] * C(c[i], now / 2 - x / 2 - 1) % M) % M;
            if (now & 1)
            {
                f[i][1] = ((long long)f[i - 1][0] * C(c[i], now / 2 - x / 2 + 1) % M + (long long)f[i - 1][1] * C(c[i], now / 2 - x / 2) % M) % M;
            }
            else
            {
                f[i][1] = 0;
            }
        }
        printf("%d\n", f[n][0]);
    }
    return 0;
}