#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=2e6+10;
int a[N],res;
int Log[N];
int c[N];
bool vis[N];
int sum,ans[N];
priority_queue<int,vector<int>,greater<int> > p;
void solve(){
	int n;cin>>n;
	while(p.size()) p.pop();
	for(int i=0;i<n;i++){
		p.push(i);
	}
	sum=0;
	for(int i=0;i<n;i++){
		int x=p.top();p.pop();
		if((sum^x)==0){
			//cout<<x<<" ";
			if(!p.size()){
				cout<<"impossible"<<endl;
				return ;
			}
			else{
				int y=p.top();p.pop();
				//cout<<y<<" ";
				ans[i]=y;
				sum^=y;
				p.push(x);
			}
		}
		else ans[i]=x,sum^=x;
	}
	for(int i=0;i<n;i++) cout<<ans[i]<<" ";
	cout<<endl;
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin>>t;
	Log[0]=1;
	for(int i=1;i<=25;i++){
		Log[i]=Log[i-1]*2;
		if(Log[i]<=1000000&&Log[i]!=2) c[Log[i]-1]=1;
	}
	while(t--) solve(); 
}