#include <algorithm>
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef map<int, int> mii;
typedef unordered_map<int, int> umii;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef vector<int> vi;
typedef vector<vector<int>> vc;
typedef vector<long long> vl;
typedef vector<vector<long long>> vll;
typedef __int128_t int128;
#define rep(x, y, z) for(int x = (y); x <= (z); x++)
#define per(x, y ,z) for(int x = (y); x >= (z); x--)
#define yes cout << "YES\n"
#define no cout << "NO\n"

//#define int long long
//const int N = 1e5 + 5;
//const int mod = 1e9 + 7;
//const ll inf = 1e18;


void solve(){
	int n; cin >> n;
	int tmp = 0;
	rep(i, 0, n - 1){
		tmp ^= i;
	}
	if(tmp == 0){
		cout << "impossible\n";
		return;
	}
	vi a;
	tmp = 0;
	rep(i, 0, n - 1){
		if((tmp ^ i) == 0){
			a.push_back(i + 1), a.push_back(i);
			tmp = tmp ^ i ^ (i + 1);
			i++;
		}
		else{
			tmp = tmp ^ i;
			a.push_back(i);
		}
	}
	for(int res : a) cout << res << ' ';
	cout << '\n';
}

signed main(){
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

	int __ = 1; cin >> __;
	while(__--){
		solve();
	}
	return 0;
}