#include <bits/stdc++.h>

using ll = long long;

void solve() {
  int n;
  std::cin >> n;
  std::vector<std::vector<int>> c(n);
  for (int i = 0; i < n; i++) {
    int a;
    std::cin >> a;
    a--;
    c[a].push_back(i);
  }

  std::vector<std::pair<int, int>> a;
  for (int i = 0; i < n; i++) {
    if (!c[i].empty()) {
      a.emplace_back(-c[i].size(), i);
    }
  }

  if (a.size() == 1) {
    std::cout << (-a[0].first) << "\n";
    return;
  }

  std::sort(a.begin(), a.end());
  auto [x, px] = a[0];
  x = -x;
  int j;
  for (j = 1; j < a.size(); j++) {
    if (a[j].first != -x) {
      break;
    } 
  }
  if (j == a.size()) j--;
  auto [y, py] = a[j];
  y = -y;

  int ans = x | y;
  int len = 1;
  while ((len * 2) <= y) {
    len *= 2;
  }
  len -= 1;

  // std::cout << px << " " << py << " " << len << "\n";
  for (int i = 0; i + len <= y; i++) {
    int l = (i == 0 ? 0 : c[py][i - 1] + 1);
    int r = (i + len == y ? n : c[py][i + len]);
    auto p = std::lower_bound(c[px].begin(), c[px].end(), l) - c[px].begin();
    int cnt = 0;
    for (int j = p; j < x; j++) {
      if (c[px][j] >= r) break;
      cnt += 1;
    }
    // std::cout << l << " " << r << " " << cnt << "\n";
    ans = std::max(ans, cnt | len);
  }
  std::swap(x, y);
  std::swap(px, py);
  len = 1;
  while ((len * 2) <= y) {
    len *= 2;
  }
  len -= 1;

  for (int i = 0; i + len <= y; i++) {
    int l = (i == 0 ? 0 : c[py][i - 1] + 1);
    int r = (i + len == y ? n : c[py][i + len]);
    auto p = std::lower_bound(c[px].begin(), c[px].end(), l) - c[px].begin();
    int cnt = 0;
    for (int j = p; j < x; j++) {
      if (c[px][j] >= r) break;
      cnt += 1;
    }
    ans = std::max(ans, cnt | len);
  }
  std::cout << ans << "\n";
}

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int t;
  std::cin >> t;
  while (t--) {
    solve();
  }    
  return 0;
}