#include <bits/stdc++.h>   using namespace std;   int a[1000000], psum[1000000];   map<long long, long long> mp, pp;   vector<long long> v;   int main() {     std::ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     ;     long long t;     cin >> t;     while (t--) {       int n, k;       cin >> n >> k;       for (int i = 0; i < n; i++) cin >> a[i];       for (int i = 0; i < (2 * k + 2); i++) {         psum[i] = 0;       }       for (int i = 0; i < n / 2; i++) {         int mn = min(a[i], a[n - i - 1]);         int mx = max(a[i], a[n - i - 1]);         psum[1] += 2;         psum[mn + 1] -= 1;         psum[mn + mx] -= 1;         psum[mx + mn + 1] += 1;         psum[mx + k + 1] += 1;       }       int ans = INT_MAX, sum = 0;       for (int i = 1; i <= (2 * k + 1); i++) psum[i] += psum[i - 1];       for (int i = 1; i < (2 * k + 1); i++) ans = min(ans, psum[i]);       cout << ans << endl;     }     return 0;   }   