#include <bits/stdc++.h>
using namespace std;

int main() {

    int t;
    cin>>t;

    while(t--)
    {
        int n;
        cin>>n;
        for(int i=2;i<=n;i+=2) cout<<i<<" "<<i-1<<" ";
        cout<<"\n";
    }
    
    return 0;
}