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#include <bits/stdc++.h>

using namespace std;

#define sim template < class c
#define ris return * this
#define dor > debug & operator <<
#define eni(x) sim > typename \
enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; };
sim > rge<c> range(c i, c j) { return {i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
~debug() { cerr << endl; }
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i)); }
sim, class b dor(pair < b, c > d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (c it = d.b; it != d.e; ++it)
    *this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
sim dor(const c&) { ris; }
#endif
};
#define imie(x...) " [" #x ": " << (x) << "] "

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
template <typename A, typename B>
using unordered_map2 = __gnu_pbds::gp_hash_table<A, B>;
using namespace __gnu_pbds;
template <typename T> using ordered_set =
  __gnu_pbds::tree<T, __gnu_pbds::null_type, less<T>, __gnu_pbds::rb_tree_tag,
                   __gnu_pbds::tree_order_statistics_node_update>;
// ordered_set<int> s; s.insert(1); s.insert(2);
// s.order_of_key(1);    // Out: 0.
// *s.find_by_order(1);  // Out: 2.

using ld = long double;
using ll = long long;

constexpr int mod = 1000 * 1000 * 1000 + 7;
constexpr int odw2 = (mod + 1) / 2;

void OdejmijOd(int& a, int b) { a -= b; if (a < 0) a += mod; }
int Odejmij(int a, int b) { OdejmijOd(a, b); return a; }
void DodajDo(int& a, int b) { a += b; if (a >= mod) a -= mod; }
int Dodaj(int a, int b) { DodajDo(a, b); return a; }
int Mnoz(int a, int b) { return (ll) a * b % mod; }
void MnozDo(int& a, int b) { a = Mnoz(a, b); }
int Pot(int a, ll b) { int res = 1; while (b) { if (b % 2 == 1) MnozDo(res, a); a = Mnoz(a, a); b /= 2; } return res; }
int Odw(int a) { return Pot(a, mod - 2); }
void PodzielDo(int& a, int b) { MnozDo(a, Odw(b)); }
int Podziel(int a, int b) { return Mnoz(a, Odw(b)); }
int Moduluj(ll x) { x %= mod; if (x < 0) x += mod; return x; }

template <typename T> T Maxi(T& a, T b) { return a = max(a, b); }
template <typename T> T Mini(T& a, T b) { return a = min(a, b); }

constexpr int MAX_FACTORIAL = 4'000'100;

class Preprocessing {
 public:
  void Run() {
    factorial.resize(MAX_FACTORIAL);
    factorial[0] = 1;
    for (int i = 1; i < MAX_FACTORIAL; i++) {
      factorial[i] = Mnoz(factorial[i - 1], i);
    }
  }

  int Factorial(int n) const {
    assert(0 <= n and n < MAX_FACTORIAL);
    return factorial[n];
  }

 private:
  vector<int> factorial;
};

// All numbers are 2.
// It means that the 2 highest values (4n and 4n-1) belong to A.
class Problem2 {
 public:
  Problem2(
    int n_,
    const Preprocessing& preprocessing_
  ) : n(n_)
    , preprocessing(preprocessing_) {}

  int Run() {
    return Dodaj(OnePlayer(), DifferentPlayers());
  }

 private:
  // If both highest values belong to one A player.
  int OnePlayer() {
    int result = 1;
    MnozDo(result, n);  // Choosing the player.
    MnozDo(result, 2);  // Choosing order of cards in this player's hand.
    MnozDo(result, preprocessing.Factorial(4 * n - 2));  // Choosing the rest of the cards for other players.
    return result;
  }

  // If both highest values belong to two different A players.
  int DifferentPlayers() {
    if (n <= 1) {
      // There must be at least 2 players.
      return 0;
    }
    int result = 1;
    MnozDo(result, n);  // Choosing the player with the highest card.
    MnozDo(result, 2);  // Choosing the position of this card in player's hand.
    MnozDo(result, n - 1);  // Choosing the second player with the second highest card.
    MnozDo(result, 2);  // Choosing the position of this card in player's hand.
    MnozDo(result, preprocessing.Factorial(4 * n - 2));  // Choosing the rest of the cards for other players.
    return result;
  }

  int n;
  const Preprocessing& preprocessing;
};

// All numbers are 1.
// It means that the highest value belongs to A/B
// and the 2nd and 3rd highest values belong to B/A.
class Problem1 {
 public:
  Problem1(
    int n_,
    const Preprocessing& preprocessing_
  ) : n(n_)
    , preprocessing(preprocessing_) {}

  int Run() {
    int result = Dodaj(OnePlayer(), DifferentPlayers());
    MnozDo(result, 2);  // Choosing whether A or B has the highest card.
    return result;
  }

 private:
  // If 2nd & 3rd highest values belong to one player (assuming B).
  int OnePlayer() {
    int result = 1;
    MnozDo(result, n);  // Choosing the player A.
    MnozDo(result, 2);  // Choosing order of cards in this player's hand.
    MnozDo(result, n);  // Choosing the player B.
    MnozDo(result, 2);  // Choosing order of cards in this player's hand.
    MnozDo(result, preprocessing.Factorial(4 * n - 3));  // Choosing the rest of the cards.
    return result;
  }

  // If 2nd & 3rd highest values belong to two different players (assuming B).
  int DifferentPlayers() {
    if (n <= 1) {
      // There must be at least 2 players.
      return 0;
    }
    int result = 1;
    MnozDo(result, n);  // Choosing the player A.
    MnozDo(result, 2);  // Choosing order of cards in this player's hand.
    MnozDo(result, n);  // Choosing the first player B.
    MnozDo(result, 2);  // Choosing order of cards in this player's hand.
    MnozDo(result, n - 1);  // Choosing the second player B.
    MnozDo(result, 2);  // Choosing order of cards in this player's hand.
    MnozDo(result, preprocessing.Factorial(4 * n - 3));  // Choosing the rest of the cards.
    return result;
  }

  int n;
  const Preprocessing& preprocessing;
};

class Problem21 {
 public:
  Problem21(
    int n_,
    vector<int> vals_,
    const Preprocessing& preprocessing_
  ) : n(n_)
    , vals(move(vals_))
    , preprocessing(preprocessing_) {}

  int Run() {
    debug() << imie(n) imie(vals);

    assert((int) vals.size() == 2 * n);
    bool has_1 = false;
    bool has_2 = false;
    for (int i = 0; i < 2 * n; i++) {
      assert(vals[i] == 1 or vals[i] == 2);
      if (vals[i] == 1) {
        has_1 = true;
      }
      if (vals[i] == 2) {
        has_2 = true;
      }
    }
    assert(has_1);
    assert(has_2);
    for (int i = 0; i + 1 < 2 * n; i++) {
      if (vals[i] == 2 and vals[i + 1] == 1) {
        if (i % 2 != 0) {
          return 0;
        }
      }
      if (vals[i] == 1 and vals[i + 1] == 2) {
        if (i % 2 != 1) {
          return 0;
        }
      }
    }

    vector<pair<int, int>> groups;
    for (int i = 0; i < 2 * n; i++) {
      if (!groups.empty() and groups.back().first == vals[i]) {
        groups.back().second++;
      } else {
        groups.emplace_back(vals[i], 1);
      }
    }

    assert(n >= 1);
    assert(!groups.empty());
    if (groups[0].first == groups.back().first) {
      groups[0].second += groups.back().second;
      groups.pop_back();
    }

    for (const auto& [type, size] : groups) {
      if (size % 2 != 1) {
        debug() << "Rejecting due to even group size.";
        return 0;
      }
    }

    const int m = (int) groups.size();
    assert(m >= 1);
    assert(m % 2 == 0);
    const int g2_count = m / 2;

    debug() << imie(groups);
    debug() << imie(g2_count);

    int result = 0;
    for (const auto& [type, size] : groups) {
      debug() << "-----------------------------------------------------------------";
      debug() << imie(type) imie(size);
      if (type == 1) {
        for (int i = 2; i < size; i += 2) {
          debug() << imie(i);
          const int value = EndingNotAtTheEndOfGroup1(i, g2_count);
          debug() << imie(i) imie(value);
          DodajDo(result, value);
        }
      } else if (type == 2) {
        const int value = EndingOnRight1Border(size, g2_count);
        debug() << imie(value);
        DodajDo(result, value);
      } else {
        assert(false);
      }
    }
    return result;
  }

 private:
  int EndingOnRight1Border(int first_g2_size, int g2_count) {
    debug() << "EndingOnRigh1Border(" imie(first_g2_size) imie(g2_count) ")";

    // The positions and values are chosen, but we still have to choose the position of cards in hands of players.
    const int prefix = Pot(2, g2_count * 2);
    debug() << imie(prefix);

    assert(first_g2_size % 2 == 1);
    const int choices_for_early_a = first_g2_size / 2;  // Number of As in the first group of 2s.
    debug() << imie(choices_for_early_a);

    // First case when the last (g2_count'th) B is covered with a later A.
    const int case_1 = Mnoz(
      ChoosePlayerForCard(g2_count, n - choices_for_early_a - g2_count),
      AssignRemaining(2 * g2_count + 1)
    );
    debug() << imie(case_1);

    // Second case when the last (g2_count'th) B is covered with an earlier A and then another A again.
    int case_2 = 0;
    if (choices_for_early_a > 0) {
      case_2 = Mnoz(
        Mnoz(
          ChoosePlayerForCard(0, choices_for_early_a),
          ChoosePlayerForCard(g2_count + 1, n - g2_count - 1)
        ),
        AssignRemaining(2 * g2_count + 2)
      );
    }
    debug() << imie(case_2);

    return Mnoz(prefix, Dodaj(case_1, case_2));
  }

  int EndingNotAtTheEndOfGroup1(int first_g1_size, int g2_count) {
    // The positions and values are chosen, but we still have to choose the position of cards in hands of players.
    const int prefix = Pot(2, g2_count * 2 + 1);

    assert(first_g1_size % 2 == 0);
    const int choices_for_early_b = first_g1_size / 2;  // Number of Bs in the first group of 1s.

    // First case when the last (g2_count+1'st) A is covered with a later B.
    const int case_1 = Mnoz(
      ChoosePlayerForCard(g2_count, n - choices_for_early_b - g2_count),
      AssignRemaining(2 * g2_count + 2)
    );

    // Second case when the last (g2_count+1'st) A is covered with an earlier B and then another B again.
    const int case_2 = Mnoz(
      Mnoz(
        ChoosePlayerForCard(0, choices_for_early_b),
        ChoosePlayerForCard(g2_count + 1, n - g2_count - 1)
      ),
      AssignRemaining(2 * g2_count + 3)
    );

    return Mnoz(prefix, Dodaj(case_1, case_2));
  }

  int ChoosePlayerForCard(int players_with_one_card, int players_with_zero_cards) {
    debug() << "ChoosePlayerForCard(" imie(players_with_one_card) imie(players_with_zero_cards) ")";
    assert(0 <= players_with_one_card and players_with_one_card <= n);
    assert(0 <= players_with_zero_cards and players_with_zero_cards <= n);
    assert(players_with_one_card + players_with_zero_cards <= n);
    return Dodaj(Mnoz(players_with_zero_cards, 2), players_with_one_card);
  }

  int AssignRemaining(int cards_taken) {
    debug() << "AssignRemaining(" imie(cards_taken) ")";
    assert(0 <= cards_taken and cards_taken <= 4 * n);
    return preprocessing.Factorial(4 * n - cards_taken);
  }

  int n;
  vector<int> vals;
  const Preprocessing& preprocessing;
};

class Problem {
 public:
  Problem(const Preprocessing& preprocessing_)
    : preprocessing(preprocessing_) {}

  int Run() {
    const int result = RunCountingCardPositions();
    #warning "Minus 1"
    if (result == -1) return -1;
    return Mnoz(result, Pot(odw2, 2 * n));
  }

 private:
  int RunCountingCardPositions() {
    cin >> n;
    vals.resize(2 * n);
    int count[3] = {0, 0, 0};
    for (int& v : vals) {
      cin >> v;
      assert(0 <= v and v <= 2);
      count[v]++;
    }
    if (count[0] > 0 and count[2] > 0) {
      return 0;
    }
    if (count[1] == 2 * n) {
      assert(count[0] == 0);
      assert(count[2] == 0);
      return Problem1(n, preprocessing).Run();
    }
    if (count[1] == 0) {
      assert(count[2] == 2 * n or count[0] == 2 * n);
      return Problem2(n, preprocessing).Run();
    }
    assert(1 <= count[1] and count[1] <= 2 * n - 1);
    if (count[2] > 0) {
      assert(count[0] == 0);
      return Problem21(n, move(vals), preprocessing).Run();
    }
    assert(count[2] == 0);
    assert(count[0] > 0);
    for (int& v : vals) {
      if (v == 0) {
        v = 2;
      }
    }
    vals.push_back(vals[0]);
    vals.erase(vals.begin());
    return Problem21(n, move(vals), preprocessing).Run();
  }

  int n;
  vector<int> vals;
  const Preprocessing& preprocessing;
};

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);

  Preprocessing preprocessing;
  preprocessing.Run();

  int t;
  cin >> t;

  for (int i = 0; i < t; i++) {
    Problem problem(preprocessing);
    cout << problem.Run() << "\n";
  }
  return 0;
}