#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long a[505], ar[505], num[505], b[505];
bool used[505];
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    vector<long long> ans;
    memset(num, 0, sizeof(num));
    memset(used, 0, sizeof(used));
    bool swi = false;
    long long swa1, swa2;
    for (long long i = 0; i < n; i++) cin >> ar[i];
    for (long long i = 0; i < n; i++) {
      if (num[ar[i]]) {
        swi = true;
        swa1 = num[ar[i]] - 1, swa2 = i;
        break;
      }
      num[ar[i]] = i + 1;
    }
    for (long long i = 0; i < n; i++) {
      long long p, mi = 501;
      for (long long j = 0; j < n; j++)
        if (!used[j] && ar[j] < mi) mi = ar[j], p = j;
      a[p] = i + 1;
      b[p] = i + 1;
      used[p] = true;
    }
    long long N = n;
    while (n > 3) {
      long long p, ma = 0;
      for (long long i = 0; i < n; i++)
        if (a[i] > ma) ma = a[i], p = i;
      while (p < n - 3) {
        ans.push_back(p + 1);
        long long tem = a[p + 2];
        a[p + 2] = a[p + 1];
        a[p + 1] = a[p];
        a[p] = tem;
        p++;
      }
      while (p < n - 1) {
        ans.push_back(n - 2);
        long long tem = a[n - 1];
        a[n - 1] = a[n - 2];
        a[n - 2] = a[n - 3];
        a[n - 3] = tem;
        p++;
      }
      n--;
    }
    bool tag = false;
    for (long long i = 0; i < 3; i++) {
      if (a[0] <= a[1] && a[1] <= a[2]) {
        tag = true;
        break;
      }
      ans.push_back(1);
      long long tem = a[2];
      a[2] = a[1];
      a[1] = a[0];
      a[0] = tem;
    }
    if (tag) {
      cout << ((long long)ans.size()) << '\n';
      for (long long i : ans) cout << i << " ";
      cout << '\n';
      continue;
    }
    if (!swi) {
      cout << "-1" << '\n';
      continue;
    }
    ans.clear();
    n = N;
    swap(b[swa1], b[swa2]);
    for (long long i = 0; i < n; i++) a[i] = b[i];
    while (n > 3) {
      long long p, ma = 0;
      for (long long i = 0; i < n; i++)
        if (a[i] > ma) ma = a[i], p = i;
      while (p < n - 3) {
        ans.push_back(p + 1);
        long long tem = a[p + 2];
        a[p + 2] = a[p + 1];
        a[p + 1] = a[p];
        a[p] = tem;
        p++;
      }
      while (p < n - 1) {
        ans.push_back(n - 2);
        long long tem = a[n - 1];
        a[n - 1] = a[n - 2];
        a[n - 2] = a[n - 3];
        a[n - 3] = tem;
        p++;
      }
      n--;
    }
    for (long long i = 0; i < 3; i++) {
      if (a[0] <= a[1] && a[1] <= a[2]) {
        tag = true;
        break;
      }
      ans.push_back(1);
      long long tem = a[2];
      a[2] = a[1];
      a[1] = a[0];
      a[0] = tem;
    }
    if (tag) {
      cout << ((long long)ans.size()) << '\n';
      for (long long i : ans) cout << i << " ";
      cout << '\n';
    } else
      cout << "-1" << '\n';
  }
  return 0;
}
