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#include <bits/stdc++.h>

#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())

using namespace std;

#ifdef LOCAL
template<typename A, typename B>
auto&operator<<(auto&o,pair<A, B>p){return o<<"("<<p.first<<", "<<p.second<<")";}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<&","[!i++]<<e;return o<<"}";}
#define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X)
#else
#define debug(...){}
#endif

using i64 = long long;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<i64, i64>;
using vi = vector<int>;
using vll = vector<i64>;

const i64 MOD = 1'000'000'007;

void add_mod(i64 &a, i64 b) {
	a += b;
	if (a >= MOD) {
		a -= MOD;
	}
}

void sub_mod(i64 &a, i64 b) {
	a -= b;
	if (a < MOD) {
		a += MOD;
	}
}

i64 mul_mod(i64 a, i64 b) {
	return (a * b) % MOD;
}

i64 pow_mod(i64 a, i64 n) {
	i64 r = 1;
	while (n) {
		if (n % 2 == 1) {
			r = mul_mod(r, a);
		}
		n /= 2;
		a = mul_mod(a, a);
	}
	return r;
}

i64 inv_mod(i64 a) {
	return pow_mod(a, MOD - 2);
}

vll fact, inv_fact;
vll inv_val;
vll pwr2;

void PreprocBasics(int sz) {
	fact.resize(sz + 1);
	inv_fact.resize(sz + 1);
	inv_val.resize(sz + 1);
	pwr2.resize(sz + 1);

	fact[0] = 1;
	for (i64 i = 1; i <= sz; ++i) {
		fact[i] = mul_mod(fact[i - 1], i);
	}
	inv_fact.back() = inv_mod(fact.back());
	for (i64 i = sz - 1; i >= 0; --i) {
		inv_fact[i] = mul_mod(inv_fact[i + 1], i + 1);
	}

	pwr2[0] = 1;
	for (i64 i = 1; i <= sz; ++i) {
		pwr2[i] = mul_mod(pwr2[i - 1], 2);
		inv_val[i] = mul_mod(inv_fact[i], fact[i - 1]);
	}
}

struct Testcase {
	int n;
	vi seq;

	void Input() {
		cin >> n;
		seq.resize(2 * n);
		for (int &x : seq) {
			cin >> x;
		}
	}

	i64 SolveAll1() {
		i64 ans = fact[4 * n - 3];
		ans = mul_mod(ans, 2 * n);
		ans = mul_mod(ans, 2 * n);
		ans = mul_mod(ans, 2 * n - 1);
		ans = mul_mod(ans, inv_mod(pwr2[2 * n - 1]));
		return ans;
	}

	i64 SolveAll2() {
		i64 ans = fact[4 * n - 2];
		ans = mul_mod(ans, 2 * n);
		ans = mul_mod(ans, 2 * n - 1);
		ans = mul_mod(ans, inv_mod(pwr2[2 * n]));
		return ans;
	}

	i64 Solve() {
		int min_val = *min_element(ALL(seq));
		int max_val = *max_element(ALL(seq));
		if (min_val == 0 && max_val == 2) {
			return 0;
		}
		if (min_val == max_val) {
			if (min_val == 0 || min_val == 2) {
				return SolveAll2();
			} else {
				return SolveAll1();
			}
		}
		assert(max_val - min_val == 1);
		if (min_val == 0) {
			for (int &x : seq) {
				x = 2 - x;
			}
			rotate(seq.begin(), seq.begin() + 1, seq.end());
			tie(min_val, max_val) = pii{2 - max_val, 2 - min_val};
		}
		assert(min_val == 1 && max_val == 2);

		vector<int> ends[3];
		const int s = 2 * n;
		for (int i = 0; i < s; ++i) {
			if (seq[i] != seq[(i + 1) % s]) {
				ends[seq[i]].push_back(i);
			}
		}
		assert(!ends[1].empty() && !ends[2].empty());
		assert(SZ(ends[1]) == SZ(ends[2]));
		for (int loc : ends[1]) {
			if (loc % 2 != 1) {
				return 0;
			}
		}
		for (int loc : ends[2]) {
			if (loc % 2 != 0) {
				return 0;
			}
		}

		if (ends[1][0] > ends[2][0]) {
			ends[1].insert(ends[1].begin(), ends[1].back() - s);
			ends[1].pop_back();
		}

		const int k = SZ(ends[1]);
		i64 X = pwr2[2 * k];
		X = mul_mod(X, fact[4 * n - 2 * k]);
		const i64 coef_mul = mul_mod(inv_val[2 * n - k], inv_val[4 * n - 2 * k - 1]);
		i64 ans = 0;

		for (int step = 0; step < k; ++step) {
			const int Ltotal = ends[2][step] - ends[1][step];
			assert(Ltotal % 2 == 1);
			const int L = Ltotal / 2;
			const int pstep = (step + k - 1) % k;
			const int Lprev = ((ends[1][step] - ends[2][pstep] + s) % s) / 2;
			debug(X, L, Lprev);
			add_mod(ans, mul_mod(X, mul_mod(2 * n - k - 2 * L, inv_val[4 * n - 2 * k])));
			add_mod(ans, mul_mod(X, mul_mod(coef_mul, mul_mod(L, 2 * n - k - 1))));
			for (int i = 1; i <= Lprev; ++i) {
				// const int remi = Lprev - i + 1;
				int c = mul_mod(X, coef_mul);
				add_mod(ans, mul_mod(c, 2 * n - k - 2 * i));
				c = mul_mod(c, inv_val[4 * n - 2 * k - 2]);
				add_mod(ans, mul_mod(c, mul_mod(2 * i, 2 * n - k - 1)));
			}
			// add_mod(ans, mul_mod(X, mul_mod(coef_mul, mul_mod(Lprev, 2 * n - k - 1))));
			// for (int i = 1; i <= L; ++i) {
			// 	add_mod(ans, mul_mod(X, mul_mod(2 * n - k - 2 * i, coef_mul)));
			// }
		}

		ans = mul_mod(ans, inv_mod(pwr2[2 * n]));

		return ans;
	}

	void Run() {
		Input();
		cout << Solve() << "\n";
	}
};

const int MAXN = 1'000'005;

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout << fixed << setprecision(14);
	cerr << fixed << setprecision(6);

	PreprocBasics(4 * MAXN + 10);
	int t;
	cin >> t;
	while (t--) {
		Testcase{}.Run();
	}
}