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#include <bits/stdc++.h>
using namespace std;

#define int long long
const int mod = 1e9+7;
int mul(int a, int b){
    return (a*b)%mod;
}

void add(int &a, int b) {
    a += b;
    if (a >= mod) a-=mod;
}

int add2(int a, int b){
    a += b;
    if (a >= mod) a-=mod;
    return a;
}

void sub(int &a, int b){
    a -= b;
    if (a < 0) a += mod;
}

int power(int a, int b){
    if (!b) return 1ll;
    int k = power(a, b/2);
    k = mul(k, k);
    if (b&1) k = mul(k, a);
    return k;
}

void solve() {
    int n; cin >> n;
    vector<int>a(2 * n);
    vector<int>f(4 * n + 1, 1), inv(4 * n + 1, 1);
    for (int i = 1; i < (int)f.size(); i++) {
        f[i] = mul(f[i - 1], i);
        inv[i] = power(f[i], mod - 2);
    }
    auto nck = [&](int N, int K){
        if (N < K || N < 0 || K < 0) return 0ll;
        return mul(f[N], mul(inv[K], inv[N - K]));
    };
    vector<int>cnt(3);
    for (auto &x: a) {
        cin >> x;
        cnt[x]++;
    }
    if (cnt[0] > 0 && cnt[2] > 0){
        cout << "0\n";
        return;
    }
    if (cnt[2] > 0){
        for (auto &x: a) x = 2 - x;
        rotate(a.begin(), a.begin() + 1, a.end());
        cnt[0] = cnt[2];
        cnt[2] = 0;
    }
    vector<int>pot(2 * n + 1, 1);
    for (int i = 1; i < (int)pot.size(); i++) {
        pot[i] = mul(pot[i - 1], 2);
    }
    if (cnt[0] == 2 * n) {
        cout << mul(mul(2 * n, 2 * n - 1), mul(power(pot[2 * n], mod - 2), f[4 * n - 2])) << "\n";
        return;
    }
    if (cnt[1] == 2 * n) {
        cout << mul(mul(mul(n, n), f[4 * n - 2]), power(pot[2 * n - 2], mod - 2)) << "\n";
        return;
    };
    auto nxt = [&](int i){
        return i == 2 * n - 1 ? 0 : i + 1;
    };
    int L = 0;
    while (a[L + 1] == a[0]) L++;
    int R = 2 * n - 1;
    while (a[R - 1] == a.back()) R--;
    if (a[0] == a.back() && (L + R) % 2 == 1) {
        cout << "0\n";
        return;
    }
    if (a[0] != a.back() && (L % 2 == 1 || R % 2 == 0)) {
        cout << "0\n";
        return;
    }
    int ile = 1;
    for (int i = L + 2; i < R; i++) {
        if (a[i] == a[i - 1]) {
            ile++;
        } else if (i > L + 1) {
            if (ile % 2 == 0){
                cout << "0\n";
                return;
            }
            ile = 1;
        }
    }
    int zmiana = 0;
    // for (auto x: a) cout << x << " ";
    // cout << endl;
    int ans = 0;
    vector<int>nast(2 * n, -1);
    for (int i = 0; i < n; i++) {
        if (a[i] != a[nxt(i)]) {
            zmiana++;
            nast[i] = i;
        }
    }
    if (zmiana % 2 == 1) {
        cout << "0\n";
        return;
    }

    for (int rep = 0; rep < 2; rep++) {
        for (int i = 2 * n - 1; i >= 0; i--) {
            if (nast[i] == -1){
                nast[i] = nast[nxt(i)];
            }
        }
    }
    auto dlugosc = [&](int i, int j){
        if (i <= j) return j - i + 1;
        return j + 2 * n - i + 1;
    };
    cout << "1\n";
}

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int t; cin >> t;
    while (t--) {
        solve();
    }
}