#include <bits/stdc++.h>
using namespace std;
long long n;
long long a[3000];
long long pre[30][3000], suf[30][3000];
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int i, t, j;
  cin >> t;
  while (t--) {
    cin >> n;
    for (i = 0; i <= n + 1; i++)
      for (j = 1; j <= 26; j++) pre[j][i] = 0, suf[j][i] = 0;
    for (i = 1; i <= n; i++) cin >> a[i];
    for (i = 1; i <= n; i++) {
      for (j = 1; j <= 26; j++) pre[j][i] = pre[j][i - 1] + (a[i] == j);
    }
    for (i = n; i > 0; i--) {
      for (j = 1; j <= 26; j++) suf[j][i] = suf[j][i + 1] + (a[i] == j);
    }
    for (i = 1; i <= 26; i++) {
      sort(suf[i] + 1, suf[i] + n + 1);
    }
    long long ans = 0;
    for (i = 1; i <= n; i++) {
      long long sum = 0;
      for (j = 1; j <= 26; j++) {
        sum = 0;
        long long r =
            lower_bound(suf[j] + 1, suf[j] + n + 1, pre[j][i]) - suf[j];
        long long u = n - r + 1;
        if (u > i) {
          long long mx2 = 0;
          sum = pre[j][i] * 2;
          for (long long k = 1; k <= 26; k++) {
            mx2 = max(mx2, pre[k][u - 1] - pre[k][i]);
          }
          sum += mx2;
        }
        ans = max(ans, sum);
      }
    }
    if (ans == 0) ans = 1;
    cout << ans << endl;
  }
  return 0;
}
