#include <bits/stdc++.h>
using namespace std;
long long modex(long long a, long long b) {
  long long ans = 1;
  a %= 1000000007;
  ;
  if (a == 0) return 0;
  while (b > 0) {
    if (b & 1) ans = (ans * a) % 1000000007;
    ;
    b = b >> 1;
    a = (a * a) % 1000000007;
    ;
  }
  return ans;
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
void solve() {
  int n;
  cin >> n;
  int a[n];
  int count[n][27];
  for (long long i = 0; i < n; ++i) {
    for (long long j = 0; j < 27; ++j) count[i][j] = 0;
  }
  for (long long i = 0; i < n; ++i) {
    cin >> a[i];
    if (i) {
      for (long long j = 0; j < 27; ++j) {
        count[i][j] = count[i - 1][j];
      }
    }
    count[i][a[i]]++;
  }
  int ans = 0;
  for (long long i = 0; i < n; ++i) {
    for (long long j = n - 1; j >= i + 1; --j) {
      if (a[i] != a[j]) continue;
      for (long long k = 1; k < 27; ++k) {
        if (k == a[i]) continue;
        int t = count[j][k] - count[i][k];
        int first = count[i][a[i]], second = 0;
        if (j == n - 1)
          second = 1;
        else
          second = (count[n - 1][a[i]] - count[j][a[i]] + 1);
        ans = max(ans, t + 2 * min(first, second));
      }
    }
  }
  for (long long i = 0; i < 27; ++i) {
    ans = max(ans, count[n - 1][i]);
  }
  if (!ans) ans = 1;
  cout << ans << "\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int q;
  cin >> q;
  while (q--) solve();
}
