#include <bits/stdc++.h>
using namespace std;
inline int qr() {
  int f = 0, fu = 1;
  char c = getchar();
  while (c < '0' || c > '9') {
    if (c == '-') fu = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    f = (f << 3) + (f << 1) + c - 48;
    c = getchar();
  }
  return f * fu;
}
const int N = 505;
int T, n, m;
vector<int> ans, seq;
map<int, int> a;
int now;
inline void move(int x) {
  int pos;
  now++;
  if (m - now == 1) {
    if (a[1] > a[2]) {
      if (m == 2) {
        puts("-1");
        return;
      }
      if (a[2] == seq[now - 2])
        ans.push_back(now - 1);
      else {
        int j = -1;
        for (register int i = now - 2; i >= 1; --i)
          if (seq[i] == seq[i - 1]) {
            j = i + 2;
            break;
          }
        if (j == -1) {
          puts("-1");
          return;
        }
        if ((now & 1) == (j & 1)) {
          for (int i = now - 2; i >= j; i -= 2) ans.push_back(i);
          for (int i = now - 1; i >= j + 1; i -= 2) ans.push_back(i);
          ans.push_back(j - 2), ans.push_back(j - 2);
          ans.push_back(j - 1), ans.push_back(j - 1);
          for (int i = j + 1; i <= now - 1; i += 2)
            ans.push_back(i), ans.push_back(i);
          for (int i = j; i <= now - 2; i += 2)
            ans.push_back(i), ans.push_back(i);
        } else {
          for (int i = now - 1; i >= j; i -= 2) ans.push_back(i);
          for (int i = now - 1; i >= j; i -= 2) ans.push_back(i);
          ans.push_back(j - 2), ans.push_back(j - 2), ans.push_back(j - 1);
          for (int i = j; i <= now - 1; i += 2)
            ans.push_back(i), ans.push_back(i);
          for (int i = j - 1; i <= now - 2; i += 2)
            ans.push_back(i), ans.push_back(i);
        }
      }
    }
    printf("%d\n", ans.size());
    for (auto it : ans) printf("%d ", it);
    puts("");
    return;
  }
  for (register int i = 1; i <= n; ++i)
    if (a[i] == x) {
      pos = i;
      break;
    }
  n--;
  for (register int i = pos; i <= n; ++i) a[i] = a[i + 1];
  for (int i = now + pos - 3; i >= now; i -= 2) ans.push_back(i);
  if (!(pos & 1)) {
    ans.push_back(now), ans.push_back(now);
    swap(a[1], a[2]);
  }
}
int main() {
  T = qr();
  while (T--) {
    ans.clear(), seq.clear(), now = 0;
    n = qr(), m = n;
    for (register int i = 1; i <= n; ++i) a[i] = qr(), seq.push_back(a[i]);
    if (n <= 1) {
      puts("0\n");
      continue;
    }
    sort(seq.begin(), seq.end());
    for (register int i = 0; i <= m - 2; ++i) move(seq[i]);
  }
  return 0;
}
