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#include <bits/stdc++.h>

#define rep(a,b,c) for(auto a = (b); a != (c); a++)
#define repD(a,b,c) for(auto a = (b); a != (c); a--)
#define repIn(a, b) for(auto& a : (b))
#define repIn2(a, b, c) for(auto& [a, b] : (c))

constexpr bool dbg = 0;
#define DEBUG if constexpr(dbg)
#define DC DEBUG std::cerr
#define eol std::endl

#define int long long
#define ld long double
#define pb push_back

using namespace std;
#define rg ranges

constexpr int mod = 1e9 + 7, MAX = 4 * 1e6 + 7;

array<int, MAX> factArr;
int factUpTo;
int fact(int k) {
    while(factUpTo < k) factArr[factUpTo + 1] = factArr[factUpTo] * (factUpTo + 1) % mod, factUpTo++;
    return factArr[k];
}

int fastPow(int a, int x) {
    if(!x) return 1;
    auto h = fastPow(a, x / 2);
    h = h * h % mod;
    if(x & 1) h = h * a % mod;
    return h;
}

array<int, MAX> twoToArr, ovTwoToArr;
void initOvTwoTo() {
    twoToArr[0] = 1;
    rep(i, 0, MAX - 1) twoToArr[i + 1] = twoToArr[i] * 2 % mod;
    ovTwoToArr[MAX - 1] = fastPow(fastPow(2, MAX - 1), mod - 2);
    repD(i, MAX - 2, -1) ovTwoToArr[i] = ovTwoToArr[i + 1] * 2 % mod;
}

int ovTwoTo(int x) {
    return ovTwoToArr[x];
}

int twoTo(int x) {
    return twoToArr[x];
}

void solve() {
    int n;
    cin >> n;
    n *= 2;
    vector<int> v(n);
    rep(i, 0, n) cin >> v[i];
    bool tw = 0, on = 0, zr = 0;
    repIn(i, v) {
        if(i == 0) zr = 1;
        if(i == 1) on = 1;
        if(i == 2) tw = 1;
    }
    if(tw && zr) { cout << "0\n"; return; }
    if(!on) {
        int ans = ((n * (n - 1) % mod) * fact(2 * n - 2) % mod) * ovTwoTo(n) % mod;
        cout << ans << '\n';
        return;
    }
    if(!zr && !tw) {
        int ans = (((2 * n * n % mod) * (n - 1) % mod) * fact(2 * n - 3) % mod) * ovTwoTo(n) % mod;
        cout << ans << '\n';
        return;
    }
    int start = 0;
    while(start < n && (v[start] == v[(start - 1 + n) % n] || v[start] == 1)) start++;
    if(start == n) { cout << "0\n"; return; } 
    vector<int> v2;
    rep(i, start, n) v2.pb(v[i]);
    rep(i, 0, start) v2.pb(v[i]);
    if(start & 1) rep(i, 0, n) v2[i] = 2 - v2[i];
    repIn(i, v2) if(!i) { cout << "0\n"; return; }
    int prv = -1, cntPrv = 1, cntInt = 0;
    repIn(i, v2) {
        if(i != prv) {
            if(cntPrv & 1) prv = i, cntPrv = 0, cntInt++;
            else { cout << "0\n"; return; }
        }
        cntPrv++;
    }
    DEBUG {
        DC << "v2: ";
        repIn(i, v2) DC << i;
        DC << eol;
    }

    swap(v, v2);
    // kurwa wzorek TODO FIX
    int ans = 0, tmpPref = 0;
    assert(cntInt % 2 == 0);
    DC << eol;
    rep(i, 0, n) {
        if(v[i] == 2 && v[i + 1] == 1) {
            int pref = 0;
            while(i - pref + 1 && v[i - pref] == 2) pref++;
            int bPrime = pref / 2;
            bPrime *= 2;
            int b = n - bPrime - cntInt / 2;
            int rest = 2 * n - cntInt - 1;
            DC << "At i = " << i << ":    pref = " << pref << "  ;  b' = " << bPrime << "  ;  b = " << b << "  ;  rest = " << rest << "\n";
            DC << " Adding " << b << " * " << fact(rest) << '\n';
            DC << " And    " << bPrime << " * " << (b + bPrime - 1) << " * " << fact(rest - 1) << "\n";
            int twoMul = twoTo(cntInt);
            DC << " All that times 2^" << cntInt << " = " << twoMul << eol;
            int add = b * fact(rest) % mod;
            add += bPrime * (b + bPrime - 1) % mod * fact(rest - 1) % mod;
            add = add * twoMul % mod;
            DC << "  So add = " << add << eol;
            ans = (ans + add) % mod;
        }
        if(v[i] == 2) continue;
        if(tmpPref <= 1) while(i + tmpPref < n && v[i + tmpPref] == 1) tmpPref++;
        else tmpPref--;
        if(tmpPref % 2 == 1) continue;
        auto pref = tmpPref;
        auto aPrime = pref;
        auto a = n - aPrime - cntInt / 2;
        auto rest = 2 * n - cntInt - 2;
        DC << "At i = " << i << ":    pref = " << pref << "  ;  a' = " << aPrime << "  ;  a = " << a << "  ;  rest = " << rest << "\n";
        DC << " Adding " << a << " * " << fact(rest) << '\n';
        DC << " And    " << aPrime << " * " << (a + aPrime - 1) << " * " << fact(rest - 1) << "\n";
        int twoMul = twoTo(cntInt + 1);
        DC << " All that times 2^" << cntInt + 1 << " = " << twoMul << eol;
        int add = a * fact(rest) % mod;
        add += aPrime * (a + aPrime - 1) % mod * fact(rest - 1) % mod;
        add = add * twoMul % mod;
        DC << "  So add = " << add << eol;
        ans = (ans + add) % mod;
    }
    cout << ans * ovTwoTo(n) % mod << '\n';
}

int32_t main() {
    ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    factArr[0] = 1;
    initOvTwoTo();
    int t;
    cin >> t;
    while(t--) solve();
}